FileUpload help needed please

 I need your help please as i'm getting this error "Input string was not in a correct format" for the following code


If FileUpload1.HasFile Then 'Get File Name Lab_UserName.Text = User.Identity.Name Lab_StudentID.Text = CType(GV_Access.Rows(0).Cells(0).FindControl("Label_StudentID"), Label).Text.ToString Lab_Date.Text = Date.Now Lab_NextDocNumber.Text = CType(GridView_GetNextDocNumber.Rows(0).Cells(0).FindControl("Label1"), Label).Text.ToString Lab_GetDocumentTypeID.Text = DDLDocumentType.SelectedValue Lab_FileName.Text = Lab_NextDocNumber.Text & "." & Lab_StudentID.Text & "." & Lab_GetDocumentTypeID.Text & "-" & Lab_Date.Text & System.IO.Path.GetExtension(FileUpload1.FileName) 'Store the file Lab_S ...