public RowCursor Evaluate( 
   QueryDef queryDef,
   bool useRecyclingCursor
)

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 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"]);
          }
        }
      }
    }
  });
}

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)
          {
            // Handle row
          }
        }
      }
    }
  });
}

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)
          {
            // Handle row
          }
        }
      }
    }
  });
}