Hi,
Please double check your GridRelationDescriptor.ChildTableName property is same as SourceListSetEntry.Name for childTable. see the below code snippet for more details.
GridRelationDescriptor parentToChildRelationDescriptor = new GridRelationDescriptor();
parentToChildRelationDescriptor.ChildTableName = "MyChildTable"; // same as SourceListSetEntry.Name for childTable.
parentToChildRelationDescriptor.RelationKind = RelationKind.RelatedMasterDetails;
parentToChildRelationDescriptor.RelationKeys.Add("parentID", "ParentID");
// Register any DataTable/IList with SourceListSet, so that RelationDescriptor can resolve the name
this.gridGroupingControl1.Engine.SourceListSet.Add("MyParentTable", parentTable);
this.gridGroupingControl1.Engine.SourceListSet.Add("MyChildTable", childTable); //Here MyChildTable is the SourceListSetEntry.Name for childTable
Sample :
RelatedMasterDetails.zipBest regards,
Haneef