ArcGIS Pro SDK （八）地理数据库 4 查询

ArcGIS Pro SDK （八）地理数据库 4 查询

环境：Visual Studio 2022 + .NET6 + ArcGIS Pro SDK 3.0

1 使用查询筛选器搜索表

public async Task SearchingATable()
{
    try
    {
        await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
            () =>
            {
                using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
                    using (Table table = geodatabase.OpenDataset<Table>("EmployeeInfo"))
                {
                    QueryFilter queryFilter = new QueryFilter
                    {
                        WhereClause = "COSTCTRN = 'Information Technology'",
                        SubFields = "KNOWNAS, OFFICE, LOCATION",
                        PostfixClause = "ORDER BY OFFICE"
                    };

                    using (RowCursor rowCursor = table.Search(queryFilter, false))
                    {
                        while (rowCursor.MoveNext())
                        {
                            using (Row row = rowCursor.Current)
                            {
                                string location = Convert.ToString(row["LOCATION"]);
                                string knownAs = Convert.ToString(row["KNOWNAS"]);
                            }
                        }
                    }
                }
            });
    }
    catch (GeodatabaseFieldException fieldException)
    {
        // 处理字段异常
    }
    catch (Exception exception)
    {
        // 处理其他异常
    }
}

2 在表中搜索非拉丁字符

using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (Table table = geodatabase.OpenDataset<Table>("TableWithChineseCharacters"))
{
    // 错误的查询示例
    string incorrectWhereClause = "颜色 = '绿'";

    // 获取国家字符串前缀
    string nationalStringPrefix = "";
    SQLSyntax sqlSyntax = geodatabase.GetSQLSyntax();
    nationalStringPrefix = sqlSyntax.GetSupportedStrings(SQLStringType.NationalStringPrefix).First();

    // 正确的查询示例
    QueryFilter queryFilter = new QueryFilter()
    {
        WhereClause = "颜色 = " + nationalStringPrefix + "'绿'"
    };
}

3 使用一组对象 ID 搜索表

public RowCursor SearchingATable(Table table, IReadOnlyList<long> objectIDs)
{
    QueryFilter queryFilter = new QueryFilter()
    {
        ObjectIDs = objectIDs
    };

    return table.Search(queryFilter);
}

4 使用空间查询过滤器搜索要素类

public async Task SearchingAFeatureClass()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
                using (FeatureClass schoolBoundaryFeatureClass = geodatabase.OpenDataset<FeatureClass>("LocalGovernment.GDB.SchoolBoundary"))
            {
                // 使用空间查询过滤器
                SpatialQueryFilter spatialQueryFilter = new SpatialQueryFilter
                {
                    WhereClause = "DISTRCTNAME = 'Indian Prairie School District 204'",
                    FilterGeometry = new PolygonBuilderEx(
                        new List<Coordinate2D>
                        {
                            new Coordinate2D(1021880, 1867396),
                            new Coordinate2D(1028223, 1870705),
                            new Coordinate2D(1031165, 1866844),
                            new Coordinate2D(1025373, 1860501),
                            new Coordinate2D(1021788, 1863810)
                        }).ToGeometry(),
                    SpatialRelationship = SpatialRelationship.Within
                };

                using (RowCursor indianPrairieCursor = schoolBoundaryFeatureClass.Search(spatialQueryFilter, false))
                {
                    while (indianPrairieCursor.MoveNext())
                    {
                        using (Feature feature = (Feature)indianPrairieCursor.Current)
                        {
                            // 处理要素
                            Console.WriteLine(feature.GetObjectID());
                        }
                    }
                }
            }
        });
}

5 从表中选择行

public async Task SelectingRowsFromATable()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
                using (Table enterpriseTable = geodatabase.OpenDataset<Table>("LocalGovernment.GDB.piCIPCost"))
            {
                QueryFilter anotherQueryFilter = new QueryFilter { WhereClause = "FLOOR = 1 AND WING = 'E'" };

                // 选择所有匹配条目
                using (Selection anotherSelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.Normal))
                {
                }

                // 选择一个匹配条目
                using (Selection onlyOneSelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.OnlyOne))
                {
                }

                // 获取空选择集
                using (Selection emptySelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.Empty))
                {
                }

                // 选择表中所有记录
                using (Selection allRecordSelection = enterpriseTable.Select(null, SelectionType.ObjectID, SelectionOption.Normal))
                {
                }
            }
        });
}

6 从要素类中选择要素

public async Task SelectingFeaturesFromAFeatureClass()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
                using (FeatureClass enterpriseFeatureClass = geodatabase.OpenDataset<FeatureClass>("LocalGovernment.GDB.FacilitySite"))
            {
                List<Coordinate2D> newCoordinates = new List<Coordinate2D>
                {
                    new Coordinate2D(1021570, 1880583),
                    new Coordinate2D(1028730, 1880994),
                    new Coordinate2D(1029718, 1875644),
                    new Coordinate2D(1021405, 1875397)
                };

                SpatialQueryFilter spatialFilter = new SpatialQueryFilter
                {
                    WhereClause = "FCODE = 'Park'",
                    FilterGeometry = new PolygonBuilderEx(newCoordinates).ToGeometry(),
                    SpatialRelationship = SpatialRelationship.Crosses
                };

                // 选择所有匹配条目
                using (Selection anotherSelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.Normal))
                {
                }

                // 选择一个匹配条目
                using (Selection onlyOneSelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.OnlyOne))
                {
                }

                // 获取空选择集
                using (Selection emptySelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.Empty))
                {
                }

                // 选择表中所有记录
                using (Selection allRecordSelection = enterpriseFeatureClass.Select(null, SelectionType.ObjectID, SelectionOption.Normal))
                {
                }
            }
        });
}

7 获取表中当前有多少行的计数

// 调用需在 QueuedTask.Run() 内部
var table = featureLayer.GetTable();
var count = table.GetCount();

8 获取图层的特征计数

var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault();
QueuedTask.Run(() =>
               {
                   FeatureClass featureClass = lyr.GetFeatureClass();
                   long nCount = featureClass.GetCount();
               });

9 对表进行排序

public RowCursor SortWorldCities(FeatureClass worldCitiesTable)
{
    using (FeatureClassDefinition featureClassDefinition = worldCitiesTable.GetDefinition())
    {
        Field countryField = featureClassDefinition.GetFields()
            .First(x => x.Name.Equals("COUNTRY_NAME"));
        Field cityNameField = featureClassDefinition.GetFields()
            .First(x => x.Name.Equals("CITY_NAME"));

        // 创建国家字段的排序描述
        SortDescription countrySortDescription = new SortDescription(countryField);
        countrySortDescription.CaseSensitivity = CaseSensitivity.Insensitive;
        countrySortDescription.SortOrder = SortOrder.Ascending;

        // 创建城市字段的排序描述
        SortDescription citySortDescription = new SortDescription(cityNameField);
        citySortDescription.CaseSensitivity = CaseSensitivity.Insensitive;
        citySortDescription.SortOrder = SortOrder.Ascending;

        // 创建表排序描述
        TableSortDescription tableSortDescription = new TableSortDescription(
            new List<SortDescription>() { countrySortDescription, citySortDescription });

        return worldCitiesTable.Sort(tableSortDescription);
    }
}

10 计算表的统计信息

// 计算1990年和2000年人口字段的总和和平均值，并按区域分组和排序
public void CalculateStatistics(FeatureClass countryFeatureClass)
{
    using (FeatureClassDefinition featureClassDefinition = 
           countryFeatureClass.GetDefinition())
    {
        // 获取字段
        Field regionField = featureClassDefinition.GetFields()
            .First(x => x.Name.Equals("Region"));
        Field pop1990Field = featureClassDefinition.GetFields()
            .First(x => x.Name.Equals("Pop1990"));
        Field pop2000Field = featureClassDefinition.GetFields()
            .First(x => x.Name.Equals("Pop2000"));

        // 创建排序描述
        SortDescription regionSortDescription = new SortDescription(regionField);
        regionSortDescription.CaseSensitivity = CaseSensitivity.Insensitive;
        regionSortDescription.SortOrder = SortOrder.Ascending;

        TableSortDescription tableSortDescription = new TableSortDescription(
            new List<SortDescription>() { regionSortDescription });

        // 创建统计描述
        TableStatisticsDescription tableStatisticsDescription = new TableStatisticsDescription(
            new List<Field>() { pop1990Field, pop2000Field },
            new List<StatisticsFunction>() { StatisticsFunction.Sum, StatisticsFunction.Mean },
            new List<Field>() { regionField },
            tableSortDescription);

        // 计算统计信息
        using (StatisticsResult statisticsResult = 
               countryFeatureClass.CalculateStatistics(tableStatisticsDescription))
        {
            foreach (StatisticsRecord record in statisticsResult)
            {
                var region = record.GroupBy[0];
                var pop1990Sum = record[0];
                var pop1990Mean = record[1];
                var pop2000Sum = record[2];
                var pop2000Mean = record[3];
            }
        }
    }
}

11 在单个表上评估 QueryDef

public async Task SimpleQueryDef()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file"))))
            {
                QueryDef adaCompliantParksQueryDef = new QueryDef
                {
                    Tables = "Park",
                    WhereClause = "ADACOMPLY = 'Yes'",
                };

                using (RowCursor rowCursor = geodatabase.Evaluate(adaCompliantParksQueryDef, false))
                {
                    while (rowCursor.MoveNext())
                    {
                        using (Row row = rowCursor.Current)
                        {
                            Feature feature = row as Feature;
                            Geometry shape = feature.GetShape();

                            String type = Convert.ToString(row["ADACOMPLY"]); // 每行都是 "Yes"

                            try
                            {
                                Table table = row.GetTable(); // 总是抛出异常
                            }
                            catch (NotSupportedException exception)
                            {
                                // 处理不支持的异常
                            }
                        }
                    }
                }
            }
        });
}

12 使用 WHERE 子句计算连接上的 QueryDef

public async Task JoiningWithWhereQueryDef()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file"))))
            {
                QueryDef municipalEmergencyFacilitiesQueryDef = new QueryDef
                {
                    SubFields = "EmergencyFacility.OBJECTID, EmergencyFacility.Shape, EmergencyFacility.FACILITYID, FacilitySite.FACILITYID, FacilitySite.FCODE",
                    Tables = "EmergencyFacility, FacilitySite",
                    WhereClause = "EmergencyFacility.FACNAME = FacilitySite.NAME AND EmergencyFacility.JURISDICT = 'Municipal'",
                };

                using (RowCursor rowCursor = geodatabase.Evaluate(municipalEmergencyFacilitiesQueryDef, false))
                {
                    while (rowCursor.MoveNext())
                    {
                        using (Row row = rowCursor.Current)
                        {
                            Feature feature = row as Feature;
                            Geometry shape = feature.GetShape();

                            long objectID = Convert.ToInt64(row["EmergencyFacility.OBJECTID"]);
                            String featureCode = Convert.ToString(row["FacilitySite.FCODE"]);

                            IReadOnlyList<Field> fields = feature.GetFields(); // 每个子字段包含一个 ArcGIS.Core.Data.Field 对象
                        }
                    }
                }
            }
        });
}

13 在外部连接上计算 QueryDef

public async Task EvaluatingQueryDefWithOuterJoin()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file"))))
            {
                QueryDef queryDefWithLeftOuterJoin = new QueryDef
                {
                    Tables = "CommunityAddress LEFT OUTER JOIN MunicipalBoundary on CommunityAddress.Municipality = MunicipalBoundary.Name",
                    SubFields = "CommunityAddress.OBJECTID, CommunityAddress.Shape, CommunityAddress.SITEADDID, CommunityAddress.ADDRNUM, CommunityAddress.FULLNAME, CommunityAddress.FULLADDR, CommunityAddress.MUNICIPALITY, MunicipalBoundary.Name, MunicipalBoundary.MUNITYP, MunicipalBoundary.LOCALFIPS",
                };

                using (RowCursor rowCursor = geodatabase.Evaluate(queryDefWithLeftOuterJoin, false))
                {
                    while (rowCursor.MoveNext())
                    {
                        using (Row row = rowCursor.Current)
                        {
                            Feature feature = row as Feature;
                            Geometry shape = feature.GetShape();

                            int siteAddressId = Convert.ToInt32(row["CommunityAddress.SITEADDID"]);
                            String stateName = Convert.ToString(row["MunicipalBoundary.name"]);
                        }
                    }
                }
            }
        });
}

14 在内部连接上评估 QueryDef

public async Task EvaluatingQueryDefWithInnerJoin()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file"))))
            {
                QueryDef queryDef = new QueryDef()
                {
                    Tables = "People INNER JOIN States ON People.FK_STATE_ID = States.OBJECTID",
                    SubFields = "People.OBJECTID, People.First_Name, People.Last_Name, People.City, States.State_Name"
                };

                using (RowCursor cursor = geodatabase.Evaluate(queryDef))
                {
                    while (cursor.MoveNext())
                    {
                        using (Row row = cursor.Current)
                        {
                            // 处理行
                        }
                    }
                }
            }
        });
}

15 在嵌套 - INNER 和 OUTER 连接上评估 QueryDef

public async Task EvaluatingQueryDefWithNestedJoin()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(
                new DatabaseConnectionFile(new Uri("path\\to\\sde\\file"))))
            {
                QueryDef queryDef = new QueryDef()
                {
                    Tables = "((People INNER JOIN States ON People.FK_STATE_ID = States.OBJECTID) LEFT OUTER JOIN Homes ON People.OBJECTID = Homes.FK_People_ID)",
                    SubFields = "People.OBJECTID, People.First_Name, People.Last_Name, States.State_Name, Homes.Address"
                };

                using (RowCursor cursor = geodatabase.Evaluate(queryDef, false))
                {
                    while (cursor.MoveNext())
                    {
                        using (Row row = cursor.Current)
                        {
                            // 处理行
                        }
                    }
                }
            }
        });
}

16 为数据库表创建默认查询描述并获取查询描述的 ArcGIS.Core.Data.Table

public async Task DefaultQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            DatabaseConnectionProperties databaseConnectionProperties = 
                new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
            {
                AuthenticationMode = AuthenticationMode.DBMS,
                Instance = "instance",
                Database = "database",
                User = "user",
                Password = "password"
            };

            using (Database database = new Database(databaseConnectionProperties))
            {
                QueryDescription queryDescription = database.GetQueryDescription("CUSTOMERS");

                using (Table table = database.OpenTable(queryDescription))
                {
                    // 使用表
                }
            }
        });
}

17 从数据库表的自定义查询创建查询说明

public async Task CustomQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            DatabaseConnectionProperties databaseConnectionProperties = 
                new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
            {
                AuthenticationMode = AuthenticationMode.DBMS,
                Instance = "instance",
                Database = "database",
                User = "user",
                Password = "password"
            };

            using (Database database = new Database(databaseConnectionProperties))
            {
                QueryDescription queryDescription = database.GetQueryDescription("SELECT OBJECTID, Shape, FACILITYID FROM EmergencyFacility WHERE JURISDICT = 'Municipal'", "MunicipalEmergencyFacilities");

                using (Table table = database.OpenTable(queryDescription))
                {
                    // 使用表.
                }
            }
        });
}

18 从没有不可为空的唯一 id 列的联接查询创建查询说明

public async Task JoinQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            DatabaseConnectionProperties databaseConnectionProperties = 
                new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
            {
                AuthenticationMode = AuthenticationMode.DBMS,
                Instance = "instance",
                Database = "database",
                User = "user",
                Password = "password"
            };

            using (Database database = new Database(databaseConnectionProperties))
            {
                QueryDescription queryDescription = database.GetQueryDescription("SELECT BUSLINES.ID as BUSLINESID, BUSSTOPS.ID as BUSSTOPSID, BUSLINES.RTE_DESC, BUSLINES.DIR, BUSSTOPS.JURISDIC, BUSSTOPS.LOCATION, BUSSTOPS.ROUTE,BUSSTOPS.SHAPE from demosql.dbo.BUSSTOPS JOIN demosql.dbo.BUSLINES ON BUSSTOPS.ROUTE = BUSLINES.ROUTE", "BusInfo");

                queryDescription.SetObjectIDFields("BUSLINESID,BUSSTOPSID");

                using (Table table = database.OpenTable(queryDescription))
                {
                    // 使用表.
                }
            }
        });
}

19 从具有多个形状类型的数据库表的查询创建查询说明

public async Task MultiGeometryQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            DatabaseConnectionProperties databaseConnectionProperties = new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
            {
                AuthenticationMode = AuthenticationMode.DBMS,
                Instance = "instance",
                Database = "database",
                User = "user",
                Password = "password"
            };

            using (Database database = new Database(databaseConnectionProperties))
            {
                QueryDescription pointQueryDescription = database.GetQueryDescription("SELECT * FROM POINTS", "PointLayer");
                QueryDescription lineQueryDescription = database.GetQueryDescription("SELECT * FROM LINES", "LineLayer");

                using (Table pointTable = database.OpenTable(pointQueryDescription))
                {
                    // 使用点表.
                }

                using (Table lineTable = database.OpenTable(lineQueryDescription))
                {
                    // 使用线表.
                }
            }
        });
}

20 从 SQLite 数据库表的查询创建查询说明

public async Task SqliteQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Database database = new Database(new SQLiteConnectionPath(new Uri("Path\\To\\Sqlite\\Database\\USA.sqlite"))))
            {
                QueryDescription washingtonCitiesQueryDescription = database.GetQueryDescription("select OBJECTID, Shape, CITY_FIPS, CITY_NAME, STATE_FIPS, STATE_CITY, TYPE, CAPITAL from main.cities where STATE_NAME='Washington'", "WashingtonCities");

                using (Table washingtonTable = database.OpenTable(washingtonCitiesQueryDescription))
                {
                    // 使用washingtonTable。
                }
            }
        });
}

21 使用 SQLSyntax 形成与平台无关的查询

public async Task UsingSqlSyntaxToFormPlatformAgnosticQueries()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri("C:\\Data\\LocalGovernment.gdb"))))
                using (FeatureClass featureClass = geodatabase.OpenDataset<FeatureClass>("FacilitySite"))
            {
                SQLSyntax sqlSyntax = geodatabase.GetSQLSyntax();
                string substringFunctionName = sqlSyntax.GetFunctionName(SQLFunction.Substring);
                string upperFunctionName = sqlSyntax.GetFunctionName(SQLFunction.Upper);
                string substringfunction = string.Format("{0}({1}(FCODE, 1, 6)) = 'SCHOOL'", upperFunctionName, substringFunctionName);

                QueryFilter queryFilter = new QueryFilter
                {
                    WhereClause = substringfunction
                };
                using (Selection selection = featureClass.Select(queryFilter, SelectionType.ObjectID, SelectionOption.Normal))
                {
                    // 使用选择结果。
                }
            }
        });
}

22 将文件地理数据库要素类连接到具有虚拟关系类的 Oracle 数据库查询图层要素类

public async Task JoiningFileGeodatabaseFeatureClassToOracleQueryLayer()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase geodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri("C:\\Data\\LocalGovernment.gdb"))))
                using (Database database = new Database(
                    new DatabaseConnectionProperties(EnterpriseDatabaseType.Oracle)
                    {
                        AuthenticationMode = AuthenticationMode.DBMS,
                        Instance = "instance",
                        User = "user",
                        Password = "password",
                        Database = "database"
                    }))

                using (FeatureClass leftFeatureClass = geodatabase.OpenDataset<FeatureClass>("Hospital"))
                using (Table rightTable = database.OpenTable(database.GetQueryDescription("FacilitySite")))
            {
                Field originPrimaryKey = leftFeatureClass.GetDefinition().GetFields().FirstOrDefault(field => field.Name.Equals("facilityId"));
                Field destinationForeignKey = rightTable.GetDefinition().GetFields().FirstOrDefault(field => field.Name.Equals("hospitalID"));

                VirtualRelationshipClassDescription description = 
                    new VirtualRelationshipClassDescription(
                    originPrimaryKey, destinationForeignKey, RelationshipCardinality.OneToOne);

                using (RelationshipClass relationshipClass = leftFeatureClass.RelateTo(rightTable, description))
                {
                    JoinDescription joinDescription = new JoinDescription(relationshipClass)
                    {
                        JoinDirection = JoinDirection.Forward,
                        JoinType = JoinType.LeftOuterJoin
                    };

                    Join join = new Join(joinDescription);

                    using (Table joinedTable = join.GetJoinedTable())
                    {
                        // 对连接后的表执行操作。
                    }
                }
            }
        });
}

23 连接来自不同地理数据库的两个表

public async Task JoinTablesFromDifferentGeodatabases()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            using (Geodatabase sourceGeodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri("Path \\ to \\Geodatabase \\ one"))))
                using (Geodatabase destinationGeodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri("Path \\ to \\Geodatabase \\ two"))))
                using (Table sourceTable = sourceGeodatabase.OpenDataset<Table>("State"))
                using (Table destinationTable = destinationGeodatabase.OpenDataset<Table>("Cities"))
            {
                Field primaryKeyField = sourceTable.GetDefinition().GetFields().FirstOrDefault(field => field.Name.Equals("State.State_Abbreviation"));
                Field foreignKeyField = destinationTable.GetDefinition().GetFields().FirstOrDefault(field => field.Name.Equals("Cities.State"));

                VirtualRelationshipClassDescription virtualRelationshipClassDescription = new VirtualRelationshipClassDescription(primaryKeyField, foreignKeyField, RelationshipCardinality.OneToMany);

                using (RelationshipClass relationshipClass = sourceTable.RelateTo(destinationTable, virtualRelationshipClassDescription))
                {
                    JoinDescription joinDescription = new JoinDescription(relationshipClass)
                    {
                        JoinDirection = JoinDirection.Forward,
                        JoinType = JoinType.InnerJoin,
                        TargetFields = sourceTable.GetDefinition().GetFields()
                    };

                    using (Join join = new Join(joinDescription))
                    {
                        Table joinedTable = join.GetJoinedTable();

                        //处理连接后的表。例如 ..
                        using (RowCursor cursor = joinedTable.Search())
                        {
                            while (cursor.MoveNext())
                            {
                                using (Row row = cursor.Current)
                                {
                                    // 使用行数据。
                                }
                            }
                        }
                    }
                }
            }
        });
}

24 使用在地理数据库中连接两个版本化表的查询创建查询表

public async Task QueryTableJoinWithVersionedData()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(
        () =>
        {
            QueryDef queryDef = new QueryDef
            {
                Tables = "CommunityAddress JOIN MunicipalBoundary on CommunityAddress.Municipality = MunicipalBoundary.Name",
                SubFields = "CommunityAddress.OBJECTID, CommunityAddress.Shape, CommunityAddress.SITEADDID, CommunityAddress.ADDRNUM, CommunityAddress.FULLNAME, CommunityAddress.FULLADDR, CommunityAddress.MUNICIPALITY, MunicipalBoundary.Name, MunicipalBoundary.MUNITYP, MunicipalBoundary.LOCALFIPS",
            };

            using (Geodatabase testVersion1Geodatabase = new Geodatabase(
                new DatabaseConnectionProperties(EnterpriseDatabaseType.Oracle)
                {
                    AuthenticationMode = AuthenticationMode.DBMS,
                    Instance = "instance",
                    User = "user",
                    Password = "password",
                    Database = "database",
                    Version = "user.testVersion1"
                }))
            {
                QueryTableDescription queryTableDescription = new QueryTableDescription(queryDef)
                {
                    Name = "CommunityAddrJounMunicipalBoundr",
                    PrimaryKeys = testVersion1Geodatabase.GetSQLSyntax().QualifyColumnName("CommunityAddress", "OBJECTID")
                };

                // 将基于testVersion1。
                using (Table queryTable = testVersion1Geodatabase.OpenQueryTable(queryTableDescription))
                {
                    // 使用queryTable。
                }
            }

            using (Geodatabase testVersion2Geodatabase = new Geodatabase(
                new DatabaseConnectionProperties(EnterpriseDatabaseType.Oracle)
                {
                    AuthenticationMode = AuthenticationMode.DBMS,
                    Instance = "instance",
                    User = "user",
                    Password = "password",
                    Database = "database",
                    Version = "user.testVersion2"
                }))
            {
                QueryTableDescription queryTableDescription = new QueryTableDescription(queryDef)
                {
                    Name = "CommunityAddrJounMunicipalBoundr",
                    PrimaryKeys = testVersion2Geodatabase.GetSQLSyntax().QualifyColumnName("CommunityAddress", "OBJECTID")
                };

                // 将基于testVersion2。
                using (Table queryTable = testVersion2Geodatabase.OpenQueryTable(queryTableDescription))
                {
                    // 使用queryTable。
                }
            }
        });
}

25 检查字段值是否为空

var val = row[field.Name];
if (val is DBNull || val == null)
{
    // 字段值为空
}
else
{
    // 字段值不为空
}

26 从字段中获取域字符串

public string GetDomainStringFromField(Row row, Field field)
{
    // 从Row中获取表和表定义
    using (Table table = row.GetTable())
        using (TableDefinition tableDefinition = table.GetDefinition())
    {
        // 获取子类型字段的名称
        string subtypeFieldName = tableDefinition.GetSubtypeField();

        // 获取子类型，如果有的话
        Subtype subtype = null;

        if (subtypeFieldName.Length != 0)
        {
            // 获取此行的子类型字段的值
            var varSubtypeCode = row[subtypeFieldName];
            long subtypeCode = (long)varSubtypeCode;

            // 获取此行的子类型
            subtype = tableDefinition.GetSubtypes().First(x => x.GetCode() == subtypeCode);
        }

        // 获取此字段的编码值域
        CodedValueDomain domain = field.GetDomain(subtype) as CodedValueDomain;

        // 返回此字段的文本字符串
        if (domain != null)
        {
            return domain.GetName(row[field.Name]);
        }
        else
        {
            return row[field.Name].ToString();
        }
    }
}