C# - TextBox验证

Question

我有一些代码检查并确保当用户在字段中输入时必须输入1到10的整数.

虽然如果用户关注该字段,但"坏"数据(例如"fdgfdg")仍然留在该字段中.因此,有些人可以演示当焦点在场上丢失时,如果数据无效,则输入默认值,例如5

private void textBox4_TextChanged(object sender, EventArgs e)
        {
            try
            {
                int numberEntered = int.Parse(textBox4.Text);
                if (numberEntered < 1 || numberEntered > 10)
                {
                    MessageBox.Show("You must enter a number between 1 and 10");
                }
            }
            catch (FormatException)
            {

                MessageBox.Show("You need to enter an integer");
            }
        }

Answer 1

有迹象表明,你可以在这里使用的几个事件,Leave,LostFocus并Validating没有对这些不同事件的更多讨论MSDN这里.

在某些情况下,Leave并且LostFocus不会触发,因此在您的情况下最好使用的是Validating事件:

    textBox1.Validating += new CancelEventHandler(textBox1_Validating);


    void textBox1_Validating(object sender, CancelEventArgs e)
    {
        int numberEntered;

        if (int.TryParse(textBox1.Text, out numberEntered))
        {
            if  (numberEntered < 1 || numberEntered > 10) 
            { 
                MessageBox.Show("You have to enter a number between 1 and 10");
                textBox1.Text = 5.ToString();
            }
        }
        else
        {
            MessageBox.Show("You need to enter an integer");
            textBox1.Text = 5.ToString();
        }
    }