ExecuteNonQuery：连接属性尚未初始化

我收到以下错误

ExecuteNonQuery：连接属性尚未初始化。

当运行以下代码时

Private Sub btnUpdate_Click(sender As Object, e As EventArgs) Handles btnUpdate.Click

    Using con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\Comp-296\Project1\Project1\Game_time.mdb")

        Using cmd = New OleDbCommand("UPDATE User-scores SET User_Name = @User_Name Game_Name = @Game_Name Score = @Score, [Time/Date] = @dt")

            con.Open()
            cmd.Parameters.Add("@User_Name", OleDbType.VarWChar).Value = txtUser.Text
            cmd.Parameters.Add("@Game_Name", OleDbType.VarWChar).Value = txtGame.Text
            cmd.Parameters.Add("@Score", OleDbType.VarWChar).Value = txtScore.Text
            cmd.Parameters.Add("@dt", OleDbType.Date).Value = Convert.ToDateTime(txtDate.Text)

            cmd.ExecuteNonQuery()

            MessageBox.Show("Data Update successfully")
        End Using
    End Using

End Sub

我是否忘记在参数中添加一些内容？

您必须将连接作为参数传递给OledbCommand

只需使用以下代码

Using con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\Comp-296\Project1\Project1\Game_time.mdb") 

    Using cmd = New OleDbCommand("UPDATE [User-scores] SET [User_Name] = ?, [Game_Name] = ?, Score = ?, [Time/Date] = ? WHERE id = 1", con) 
        con.Open() 
        cmd.Parameters.Add("@p1", OleDbType.VarWChar).Value = txtUser.Text 
        cmd.Parameters.Add("@p2", OleDbType.VarWChar).Value = txtGame.Text 
        cmd.Parameters.Add("@p3", OleDbType.VarWChar).Value = txtScore.Text 
        cmd.Parameters.Add("@p4", OleDbType.Date).Value = Convert.ToDateTime(txtDate.Text) 

        cmd.ExecuteNonQuery() 

        MessageBox.Show("Data Update successfully") 
    End Using 
End Using

看起来你必须使用?标记将参数传递给OledbCommand （你的方法是为了SQLCommand)

阅读更多关于Oledb 参数 https://msdn.microsoft.com/en-us/library/system.data.oledb.oledbparameter(v=vs.110).aspx