Getting Error: collection was modified enumeration operation might not execute

[Blue Berry]

iam getting the following Error: "Collection was modified enumeration operation might not execute".My Code: \[code\] If (Not Session("MailTable") Is Nothing) Then Dim dataTable As DataTable = Session("MailTable") Dim drow() As DataRow = dataTable.Select("column1='" + txtVerEmail.Text + "'") If (drow.Count <> 0) Then ResourcesList.Value = http://stackoverflow.com/questions/12689697/drow(0).Item(1) +";" Else ResourcesList.Value = http://stackoverflow.com/questions/12689697/txtVerEmail.Text +";" End If Else ResourcesList.Value = http://stackoverflow.com/questions/12689697/txtVerEmail.Text +";" End If\[/code\]I have also done a screenshot of the Error: ErrorWhat does the Error mean and how can i fix it?Thanks