visual basic linked to access database

[salehamr]

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left]Dim objConnect As OleDbConnection

Dim objCommand As OleDbCommand

objConnect = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;data source =supermarket2003.mdb")

objConnect.Open()

Dim sql As String

txtnum هو عبارة عن textbox في شاشة الvb و item_name, item_no هو اسم fields في جدول ال product

sql = "SELECT item_name FROM product where item_no = txtnum.text"

objCommand = New OleDbCommand(sql, objConnect)

Dim objReader As OleDbDataReader = objCommand.ExecuteReader[/left

عندما يصل الى هذه الجملة يعطي الخطأ التالي = No value given for one or more required parameters]