Question

Im trying to connect MySql from VB.NET in visual basic 2010. I wanted to query the db just to get one return is response to my proID once I click the button. it successfully show connection has been establish but I can’t seems to run any sql query on it. what might have been wrong?

This is the error I got from immediate window:

A first chance exception of type 'System.InvalidOperationException' occurred in MySql.Data.dll

Lets assume num is 1001 from the keypress event.

Public Class Form1
    Private connStr As String = "server=localhost;" & _
                "user id=root;Password=1234561;" & _
                "database = test"
    Dim num As Integer


Private Sub TextBox1_keypress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
    Dim str As String
    If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Enter) Then
        str = TextBox1.Text
        Dim splitVals As String() = str.Split(" ")
        num = splitVals(1)
    End If
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim query As String = "SELECT * FROM products"
    Dim con As New MySqlConnection(connStr)
    Dim cmd As New MySqlCommand(query)
    Try
        con.Open()
        MessageBox.Show("Database Connected")
        cmd.ExecuteNonQuery()
        cmd.Connection.Close()

        con.Close()
    Catch ex As Exception
        Console.WriteLine(ex.Message)
    End Try
End Sub

End Class

Answer 1

ExecuteNonQuery is used for SQL statements that don’t return any data (For example, INSERT, UPDATE, DELETE).

What do you want to achieve? If you want to fetch all records from product table and display it on a datagrid, then try this:

Using xConn as New MySqlConnection(connStr)
    Using xComm as new MySQLCommand()
        xComm.Connection = xConn
        xComm.CommandText = "SELECT * FROM products"
        Using xAdapter as new MySQLDAtaAdapter(xComm)
            Dim ds as new Dataset
            xConn.Open()
            xAdapter.Fill(ds)
            datagridview1.datasource = ds.tables(0)
        End Using
    End Using
End Using

UPDATE 1

Dim xPrice as Integer = 0
Using xConn as New MySqlConnection(connStr)
    Using xComm as new MySQLCommand()
        xComm.Connection = xConn
        xComm.CommandText = "SELECT ProductPrice FROM products WHERE proID = @xID"
            xComm.Parameters.AddWithValue("xID", "Value Here")
            xConn.Open()
            xPrice = CInt(xComm.ExecuteScalar())
            xConn.Close
    End Using
End Using

Msgbox xPrice