Conversion from type 'Button' to type string is not valid

Question

I am having trouble with some code. I have created a form and all I want to do is run a query when the button is pressed and enter the outcome into the text box.

But I keep getting an error. Here is my code:

Public Sub getdn_Click(Query As Object, e As EventArgs) Handles getdn.Click
    Try
        SQLCon.Open()

        SQLCmd = New SqlCommand(CStr(Query), SQLCon)

        ' build the query
        SQLCmd.CommandText = "Select Top 1 docnumber+1 From transportreq Order By Docnumber Desc"
        ' run the query and obtain a reader to get the results
        Dim R As SqlDataReader = SQLCmd.ExecuteReader()

        ' check if there are results
        If (R.Read()) Then
            ' populate the values of the controls
            dnText.Text = CStr(R(0))
        End If

        SQLCon.Close()
    Catch ex As Exception
        MsgBox(ex.Message, MsgBoxStyle.Critical, "SQL Error")

        If SQLCon.State = ConnectionState.Open Then
            SQLCon.Close()
        End If
    End Try
End Sub

The error message is self-explainable. You're trying to convert a Button to a String. Replace CStr(Query) with "" and rename Query to sender. — Bjørn-Roger Kringsjå
– Bjørn-Roger Kringsjå, Commented Dec 15, 2014 at 11:00
This seems to be the event handler of a button object. In this case the Query parameter is the button pressed. Clearly this is not a string and trying to convert it to a string (CStr(Query)) is useless. — Steve
– Steve, Commented Dec 15, 2014 at 11:00

Steve · Accepted Answer · 2014-12-15 11:01:47Z

1

This seems to be the event handler of a button object. In this case the Query parameter is the button pressed. Clearly this is not a string and trying to convert it to a string (CStr(Query)) is useless. Instead you have your query assigned to the CommandText of the SqlCommand object.

So perhaps your code should look like this

Public Sub getdn_Click(sender As Object, e As EventArgs) Handles getdn.Click
    Try
        SQLCon.Open()

        Dim Query = "Select Top 1 docnumber+1 From transportreq Order By Docnumber Desc"
        SQLCmd = New SqlCommand(Query, SQLCon)
        Dim R As SqlDataReader = SQLCmd.ExecuteReader()
        If (R.Read()) Then
            dnText.Text = CStr(R(0))
        End If

        SQLCon.Close()
    Catch ex As Exception
        MsgBox(ex.Message, MsgBoxStyle.Critical, "SQL Error")

        If SQLCon.State = ConnectionState.Open Then
            SQLCon.Close()
        End If
    End Try
End Sub

answered Dec 15, 2014 at 11:01

Steve

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1 Comment

Danny Broadhurst Over a year ago

Perfect!!New it was something simple.

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