Function which returns datatable

Question

I have a function which returns datatable

  Private Function _Read() As DataTable
    Dim _cmd As New SqlCommand
    Dim _da As New SqlDataAdapter(_cmd)
    Dim _dt As New DataTable
    With _cmd
        .Connection = dbRoot
        .CommandTimeout = 0
        .CommandText = "SELECT * FROM Table "
    End With

    Try
        _da.Fill(_dt)
        Return _dt
    Catch ex As Exception
        Return Nothing
    End Try

End Function

Now i want to get control if error ocurs so i put the code inside the Try Catch block.

How can i check from my program did exception happend ?

Can i set like this

IF _Read = nothing ?

`returnedDT = _Read() // If returnedDT IsNot Nothing Then...` — Ňɏssa Pøngjǣrdenlarp, Dec 01 '15 at 13:53

score 1 · Accepted Answer · edited May 23 '17 at 10:27

1

First, to check if _Read returned nothing, you have to use the Is keyword in vb.net :

If _Read Is nothing Then
...
End if

But If you really want to "get control if error occurs" then the first thing you have to do is apply proper error handling. Never catch and ignore exceptions. A way to handle the exception is to notify the user through a message box, log it. Another option is not to have a Catch in the procedure so that the error is propagated up the stack.

Also, you may want to have a finally block to close and release resources, or use a using construct. See here : SqlCommand (Using Statement / Disposing issue)

edited May 23 '17 at 10:27

Community

1
1

answered Dec 01 '15 at 08:01

chrisl08

1,658
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How can i set if its not nothing ? – myString Dec 01 '15 at 10:43
If _Read IsNot Nothing Then – chrisl08 Dec 01 '15 at 20:08

score 1 · Answer 2 · answered Dec 01 '15 at 08:47

Try below variation of _Read method. This method returns DataTable as return type and error message as output parameter. I hope this will help.

Private Function _Read(ByRef errorMsg As String) As DataTable

    Try
        'Get data from datrabase

        'return datatable
        _Read = New Data.DataTable

        'return empty if no error occured
        errorMsg = ""

    Catch ex As Exception

        'return null data table
        _Read = Nothing

        'return error code
        errorMsg = ex.Message

    End Try

End Function

Call this method in you code as

    Dim myDataTable As Data.DataTable
    Dim myErrorMsg As String = ""

    myDataTable = _Read(myErrorMsg)

    If myErrorMsg <> "" Then
        MessageBox.Show(myErrorMsg)
    End If

Function which returns datatable

2 Answers2