C# 在添加/保存之前，检查db中是否已经存在值并绑定dgv

我有一个绑定的datagridview，我想在插入用户名之前检查该用户名是否已经存在于我的数据库中。我通过文本框向dgv和数据库插入值。提前谢谢

    private void user1BindingNavigatorSaveItem_Click(object sender, EventArgs e)
    {
        this.Validate();
        this.user1BindingSource2.EndEdit();
        this.tableAdapterManager2.UpdateAll(this.databasDataSet);

    }

    private void Form2_Load(object sender, EventArgs e)
    {
        // TODO: This line of code loads data into the 'databasDataSet.user1' table. You can move, or remove it, as needed.
        this.user1TableAdapter2.Fill(this.databasDataSet.user1);

        user1DataGridView.Columns[0].Visible = false;
        passwordTextBox.PasswordChar ='*';

    }

    private void add_new_button_Click(object sender, EventArgs e)
    {

            this.user1BindingSource2.AddNew();

    }

    private void save_button_Click(object sender, EventArgs e)
    {


        this.Validate();
        this.user1BindingSource2.EndEdit();
        this.tableAdapterManager2.UpdateAll(this.databasDataSet);
    }




    private void delete_button_Click(object sender, EventArgs e)
    {
        this.user1BindingSource2.RemoveCurrent();

    }

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要验证服务器端的任何内容（在您的案例中是否存在用户名），有

CustomValidator

控件。将其添加到您的页面，并将其附加到您的用户名

文本框

。然后将验证代码放入

ServerValidate

事件处理程序