The SelectCommand property has not been initialized before calling 'Fill'. in WinForm

Question

I am building a windows application using C#. In my login form, I'm getting Select Command property has not been initialized before calling fill method.

Here is the code:

public partial class frmlogin : Form
{
    SqlConnection con = new SqlConnection("Data Source=TH07L019;Initial Catalog=loginerror;Integrated Security=True");
    DataTable dt = new DataTable();
    SqlCommand cmd = new SqlCommand();
    SqlDataAdapter adp = new SqlDataAdapter();

    public frmlogin()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        cmd.Connection = con;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        con.Open();
        cmd.CommandText = "select * from login where username='" + txt1.Text + "' and password='" + txt2.Text +"'";
        adp.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            frmmain main = new frmmain();
            main.Show();
        }
        else
        {
            MessageBox.Show("Please enter correct name and passowrd", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }
}

Answer 1

Another way to accomplish would be to simply pass the SQLCommand as an argument into your data adapter as follows -

SqlCommand cmd = new SqlCommand();
SqlDataAdapter adp = new SqlDataAdapter(cmd);

Answer 2

You have to specify select command of SqlDataAdapter before filling your table. You are not doing it. Your SqlCommand object is not connected in any way to your SqlDataAdapter.

 adp.SelectCommand=cmd;