"undefined function call" when using function in a DataSet

I have a DataSet in UserAdmin.xsd with many DataTables. Most of the data come directly from stored procedures. However for one of the tables, I would like to add another column which uses a C# function defined in another file.

I put for the expression for that column: Helper.ObtainUserInfo(user_nm, "displayname"); but that gives me an error "undefined function call".

Helper.cs is located under App_Code/Common/ and the namespace is COM.A.B.C. UserAd开发者_C百科min.xsd is located under App_Code/.

How can I access the function ObtainUserInfo()? Is there something like a using keyword that I could use?

You cannot use DataColumn.Expression to call a .NET-Method to obtain a value. You must refer a column in this table or one of the parent/child tables to calculate the value. For more informations on what you can('t) do with Expressions look here: http://msdn.microsoft.com/en-us/library/system.data.datacolumn.expression%28v=VS.100%29.aspx

Instead of using a method or an expression, i would recommend to do this with SQL whenever possible.

if You provide your code, then it would be very helpful to solve your problem, anyway assuming your problem i have solution, i hope it may helped you

You can open the Code File Which Contain ObtainUserInfo() Function, then You can Refer that Class Name, in other File. For eg : If you hav solution Named WebApplication1, inside that if you have users class, in that users class, ObtainUserinfo() function is defined, then You Have to Use statement like this,

Using WebApplication1.Users