مشکل در asp ویژال 2013

[hamix666]

An exception of type 'System.ArgumentException' occurred in System.Data.dll but was not handled in user code


Additional information: Column 'username' does not belong to table .




System.ArgumentException was unhandled by user code
HResult=-2147024809
Message=Column 'username' does not belong to table .
Source=System.Data
StackTrace:
at System.Data.DataRow.GetDataColumn(String columnName)
at System.Data.DataRow.get_Item(String columnName)
at _Default.Page_Load(Object sender, EventArgs e) in e:\proje\parsCMS\parsCMS\Default.aspx.cs:line 29
at System.Web.Util.CalliEventHandlerDelegateProxy.Cal lback(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException:

علت این مشکل چیه؟