How do I track down an Unclosed reader - sql

Question

I've got a utility function in a much larger project that updates a backend SQL database. It's currently failing most times I use it, with the error:
There is already an open DataReader associated with this Command which must be closed first.
The code for the function is below:
Public Function Update_Data(what As String, Optional where As String = "",
Optional table As String = ThisAddIn.defaultTable) As Integer
Try
Dim cmd As New SqlCommand With {
.Connection = conn
}
cmd.CommandText = "UPDATE " & table & " SET " & what
If where <> "" Then
cmd.CommandText &= " WHERE " & where
End If
Update_Data = cmd.ExecuteNonQuery
cmd.Dispose()
Catch ex As Exception
Update_Data = 0
Debug.WriteLine("SQL Error updating data:" & vbCrLf & ex.Message)
End Try
End Function
I've gone through the rest of the code to make sure that whenever I have a SQLDataReader declared I later call reader.close(). I added the cmd.Dispose() line to this and all the other ExecuteNonQuery functions I could find - incase that helped?
Are there any other instances/types of reader that might not be being closed?

Answer 1

In the case of an Exception, you aren't disposing your command.
If you don't want to use Using, add a Finally
Public Function Update_Data(what As String, Optional where As String = "",
Optional table As String = ThisAddIn.defaultTable) As Integer
Dim cmd As SqlCommand
Try
cmd = New SqlCommand With {.Connection = conn}
cmd.CommandText = "UPDATE " & table & " SET " & what
If where <> "" Then
cmd.CommandText &= " WHERE " & where
End If
Update_Data = cmd.ExecuteNonQuery
Catch ex As Exception
Update_Data = 0
Debug.WriteLine("SQL Error updating data:" & vbCrLf & ex.Message)
Finally
cmd.Dispose()
End Try
End Function
but Using might be simpler
Public Function Update_Data(what As String, Optional where As String = "",
Optional table As String = ThisAddIn.defaultTable) As Integer
Using cmd As New SqlCommand With {.Connection = conn}
Try
cmd.CommandText = "UPDATE " & table & " SET " & what
If where <> "" Then
cmd.CommandText &= " WHERE " & where
End If
Update_Data = cmd.ExecuteNonQuery
Catch ex As Exception
Update_Data = 0
Debug.WriteLine("SQL Error updating data:" & vbCrLf & ex.Message)
End Try
End Using
End Function