在添加/保存之前，请检查db中是否存在值并绑定dgv

Question

I have a bound datagridview and I want to check before inserting a username if that username already exists or not in my database. I insert values to dgv and database through a textBox. Thanks in advance..

    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();

    }

Answer 1

To validate anything on the server-side (the existence of the username in your case) there is CustomValidator control. Add it to your page and attach it to your username TextBox . Then place your validation code to ServerValidate event handler.