Question

如果文本框为空，并且我将数据插入数据库，那么如何显示消息框？

private void button1_Click(object sender, EventArgs e)
{
    try
    {
        connection.Open();
        OleDbCommand command = new OleDbCommand();
        command.Connection = connection;
        command.CommandText = "insert into Ученики (Имя,Класс,Группа) values ('" + textBox2.Text + "','" + comboBox1.Text + "','" + comboBox2.Text + "')";
        command.ExecuteNonQuery();
        MessageBox.Show("Data Saved");
        connection.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error " + ex);
    }
}

Answer 1

检查文本框的值是否为空：

private void button1_Click(object sender, EventArgs e)
{
    if (String.IsNullOrEmpty(textBox2.Text)) 
    {
        try
        {
            connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            command.CommandText = "insert into Ученики (Имя,Класс,Группа) values ('" + textBox2.Text + "','" + comboBox1.Text + "','" + comboBox2.Text + "')";
            command.ExecuteNonQuery();
            MessageBox.Show("Data Saved");
            connection.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error " + ex);
        }
    }
    else
    {
        MessageBox.Show("textbox2 was empty!");
    }
}

Answer 2

您可以检查每个文本框是否有值。

private void button1_Click()
{
    if (string.IsNullOrEmpty(textBox2.Text) || string.IsNullOrEmpty(comboBox1.Text) || string.IsNullOrEmpty(comboBox2.Text)
    { 
        MesageBox.Show(@"Please enter text into each box.");
        return;
    }

    // if all textboxes have values then call update the database
}

Answer 3

您也可以使用javascript调用提醒框。

ASPX页面：

    <script type="text/javascript" language="javascript">
function checkTextBoxEmpty() {
    if (document.getElementById('<%=TextBox1.ClientId %>').value == "") {
        alert("TextBox Empty.");
    }
}
</script>
<asp:TextBox ID="TextBox1" runat="server" />
<asp:Button ID="Button1" runat="server" />

代码背后：

private void Page_Load(object sender, EventArgs e)
{
    Button1.Attributes.Add("onClick", "javascript:checkTextBoxEmpty();")
}

private void Button1_Click(object sender, EventArgs e)
{
    try
    {
        connection.Open();
        OleDbCommand command = new OleDbCommand();
        command.Connection = connection;
        command.CommandText = "insert into Ученики (Имя,Класс,Группа) values ('" + textBox2.Text + "','" + comboBox1.Text + "','" + comboBox2.Text + "')";
        command.ExecuteNonQuery();
        MessageBox.Show("Data Saved");
        connection.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error " + ex);
    }
}

C＃数据库插入数据

3 个答案: