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copied!<p>Pretty much what the error message implies - the Connection property of the SqlCommand object hasn't been assigned to the connection you opened (in this case you called it <code>myConnection</code>).</p> <p>Also, a word of advice here. Do some reading on sql parameters - doing sql concatenation from user input without any sanity checks is the way <a href="http://en.wikipedia.org/wiki/SQL_injection" rel="nofollow">SQL injection</a> attacks happen. </p> <p>This is one way to do it:</p> <pre><code>Private Sub cmdAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAdd.Click Try myConnection.Open() myCommand = New SqlCommand( _ "INSERT INTO tblBook(BookCode, BookTitle, Author, PublishingYear, Price, " & _ " EnterDate, CatID, RackID, Amount) " & _ "VALUES(@bookCode, @bookTitle, @author, @publishingYear, @price, @enterDate, " & _ " @catId, @rackId, @amount)") myCommand.Connection = myConnection with myCommand.Parameters .AddWithValue("bookCode", txtBookCode.Text) .AddWithValue("bookTitle", txtTitle.Text) .AddWithValue("author", txtAuthor.Text) .AddWithValue("publishingYear", txtPublishYear.Text) .AddWithValue("price", txtPrice.Text) .AddWithValue("enterDate", txtEnterDate.Text) .AddWithValue("catId", txtCategory.Text) .AddWithValue("rackId", txtRack.Text) .AddWithValue("amount", txtAmount.Text) end with myCommand.ExecuteNonQuery() MsgBox("The book named '" & txtTitle.Text & "' has been inseted successfully") ClearBox() Catch ex As Exception MsgBox(ex.Message()) End Try myConnection.Close() End Sub </code></pre>

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