Sign In Code in ASP.Net

First Insert these lines at the top of your code bind file.

using System.Data;

using System.Configuration;

using System.Data.SqlClient;

Second step is to write this code in signin button event

protected void btnSignIn_Click(object sender, EventArgs e)
    {
        String struserid = txtuserid.Text;
        String strpassword = txtpassword.Text;
        if (struserid == "" && strpassword == "")
        {
            Label1.Text = "Please Valid User ID";
            Label2.Text = "Please Fill Valid Password";
        }
        else
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = _connStr;
            String strselect = "select userid,password from profiledata where userid='" + struserid + "' and password='" + strpassword + "'";
            con.Open();
            SqlCommand cmd = new SqlCommand(strselect,con);
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                Session["sessionuserId"] = struserid;
                ScriptManager.RegisterStartupScript(Page, typeof(Page), "OpenWindow", "window.open('mygallary.aspx','frame1');", true);
             
            }
            else
            {
                Label1.Text = "Please Valid User ID";
                Label2.Text = "Please Fill Valid Password";
         
            }

        }
    }