I&#039;m deploying simple c# asp.net application. I have one dataset with two relational data. everything looks fine, application with simple datagrid is doing well without any problem.<BR> <BR> But probles comes. When I want to modify detail table (master/detail relationship) using XML designer, my work destroy dataset which is unparsable. In detail table I add new element, call him parent_name ,<BR>and then set expresion for this new element in property window <BR><BR> Parent(Relation2).Name<BR><BR>When I save this work, an error occures. When I switch in the main form view, icon of my dataset is vanished and program is unrunable. Compiler is returning<BR><BR>C:webserverorgb40MyDataSet.xsd(1) : Custom tool error: Unable to convert input xml file content to a DataSet. Object reference not set to an instance of an object.<BR><BR>Does anybody some skillities in this ? If yes, send me please some theory about this. I&#039;m not a good programmer, and this scares me a lot. What if this is VS.NET bug ?<BR><BR>thanks