使用app.config在vb.net 2012中连接字符串以进行ms访问

Question

Hello I am a newbie in vb.net, I created a form where I need to call connection at least 4 to 5 times. So I write the connection string 4-5 times for connection. But I came to know that I can use app.config file for saving the connection string. So I tried the below code

app.config file

<?xml version="1.0" encoding="utf-8" ?>
   <configuration>
      <configSections>
      </configSections>
      <connectionStrings>
       <add name="ConString"    connectionString="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\kumar\Desktop\prodb.accdb;"/>
      </connectionStrings>
     <startup>
       <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
      </configuration>

And in vb.net form

Imports System.Configuration


Public Class form1
    Dim con As System.Data.OleDb.OleDbConnection
    Dim cmd As System.Data.OleDb.OleDbCommand
    Dim dr As System.Data.OleDb.OleDbDataReader
    Dim sqlstr As String
 Private Sub Button4_Click_1(sender As Object, e As EventArgs) Handles Button4.Click
        Dim connectionString As String = ConfigurationManager.ConnectionStrings("ConString").ConnectionString

        Try
            con = New System.Data.OleDb.OleDbConnection("connectionString")
            con.Open()
            Dim ds As DataSet = New DataSet
            Dim adapter As New OleDb.OleDbDataAdapter
            Dim sql As String
            Dim s As String
            s = txtsearch.Text
            sql = "select icode as `Item Code` , iname as `Name` ,irate as `Rate`,icomment as `Comment` from iteminfo   "

            adapter.SelectCommand = New OleDb.OleDbCommand(sql, con)
            adapter.Fill(ds)
            DataGridView1.DataSource = ds.Tables(0)
        Catch ex As Exception
            MsgBox("error found")
        End Try


    End Sub

But not able to access the data base.

I have added the reference system.configuration .

Answer 1

In this line just replace "connectionString" to connectionString con = New System.Data.OleDb.OleDbConnection("connectionString")

simply remove quotes ur problem solve...