Delete Query in Linq in asp.net

MyLinqDataClassesDataContext mylinq = new MyLinqDataClassesDataContext();

var deleteuser = from p in mylinq.userCredentials

                         where p.uname_db.Contains(TextBox3.Text)

                         select p;

    mylinq.userCredentials.DeleteAllOnSubmit(deleteuser);

    mylinq.SubmitChanges();

Insert Query in Linq in asp.net

protected void btn_insert_Click(object sender, EventArgs e)

    {

        var userInsert = new userCredential()

        {

            uname_db = TextBox1.Text,

            password_db = TextBox2.Text

        };

        mylinq.userCredentials.InsertOnSubmit(userInsert);

        mylinq.SubmitChanges(); 

    }