Logic to check username and Password

code to  check username and Password

You can do it in following way :

SqlDataAdapter objAdpt;
SqlConnection objCon = new SqlConnectin("your database connection string");
DataTable objDt;

now  in the Click event of Button say "OK" button click event..

objAdpt = new SqlDataAdapter("Select * from yourtablename WHERE UserID=' " + textBox1.Text.Trim() + " ' , Password = ' " + textBox2.Text.Trim() + " ' ", objCon);
objDt = new DataTable();
objAdpt.Fill(objDt);

if(objDt.Rows.Count > 0)
{
lblmsg.Text="you are Login";
Response.Redirect("home.aspx");
  // valid user. allow user to use system..
}
else
{
lblmsg.Text="Invalid Login";
Response.Redirect("Login.aspx");
  // put message that invalid user..
}