Question

Ok I can successfully connect to my Access database but I am still learning on how to output that data. Here is the run down.

I am designing a page where the user inputs the customer ID and then gets a list of incidents for that customer. Then I would like the user to be able to add a survey about the incident.

Problem I am running into is the ability to display this data. I have tried various method. Eventually I want to be able to display the data into a listbox and have them select it and take the survey but I am not near that far yet. Here is what I have on the connection and my attempt which doesn’t work to output the data:

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim sql As String = "SELECT [Title], [Description] FROM [Incidents] WHERE ([CustomerID] = textbox1.text)"
        Dim conn As New System.Data.OleDb.OleDbConnection()
        conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & "C:\Users\Allen PC7\Documents\Visual Studio 2008\Projects\1-A SportsPro\App_Data\TechSupport.mdb"
        Dim myCommand As New System.Data.OleDb.OleDbCommand(sql, conn)
        conn.Open()
        Dim myReader As System.Data.OleDb.OleDbDataReader = myCommand.ExecuteReader()
        Try
            While myReader.Read()
                Console.WriteLine(myReader.GetInt32(0).ToString() + ", " + myReader.GetString(1))
            End While
        Finally
            myReader.Close()
            conn.Close()
        End Try

    End Sub

I just can’t get anything displayed in the console and instead get an error saying Dim myReader As System.Data.OleDb.OleDbDataReader = myCommand.ExecuteReader()…System.Data.OleDb.OleDbException: No value given for one or more required parameters.

Thanks

Answer 1

You are not passing in a proper value to the SQL:

"SELECT [Title], [Description] FROM [Incidents] WHERE ([CustomerID] = textbox1.text)"

It will try to look for CustomerID that is equal to the database value “textbox1.text”. Since this is probably the wrong data type and a table/column that doesn’t exist, you are getting the error.

You should be using a parameterized query to avoid SQL Injection.

Dim sql As String = "SELECT [Title], [Description] FROM [Incidents] WHERE ([CustomerID] = ?)"

Dim myCommand As New System.Data.OleDb.OleDbCommand(sql, conn)
myCommand.Parameters.Add("@p1", OleDbType.Integer, 4).Value = textbox1.text

This will fail if the value in textbox1.text is not of the right type – you should both validate and convert to the right type (my code assumes an integer).