public class 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 adaCompilantParksQueryDef = new QueryDef
      {
        Tables = "Park",
        WhereClause = "ADACOMPLY = 'Yes'",
      };

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

            String type = Convert.ToString(row["ADACOMPLY"]); // will be "Yes" for each row.

            try
            {
              Table table = row.GetTable(); // Will always throw exception.
            }
            catch (NotSupportedException exception)
            {
              // Handle not supported exception.
            }
          }
        }
      }
    }
  });
}

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(); //Contains one ArcGIS.Core.Data.Field objects for every subfield
          }
        }
      }
    }
  });
}

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")
      };

      // Will be based on testVersion1.
      using (Table queryTable = testVersion1Geodatabase.OpenQueryTable(queryTableDescription))
      {
        // Use 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")
      };

      // Will be based on testVersion2.
      using (Table queryTable = testVersion2Geodatabase.OpenQueryTable(queryTableDescription))
      {
        // Use queryTable.
      }
    }
  });
}