Source: - Index and length must refer to a location within the string. Parameter name: length at System.String.InternalSubStringWithChecks(Int32 startIndex, Int32 length, Boolean fAlwaysCopy) at Client.TDI_TemplateEditor.makeConformableColumnName(String fieldName) at Client.TDI_TemplateEditor.btnAdd_Click(Object sender, EventArgs e) An error occurred adding a field to the list.