[Boris2105]

При попытке сменить пароль выдает ошибку

The property 'password' is part of the object's key information and cannot be modified.

 
private void button3_Click(object sender, EventArgs e)
        {
            string _user = txtUsername.Text;
 
            tbl_user _tbl = _dbObj.tbl_user.First(i => i.username == txtUsername.Text);
            _tbl.password = txtPassword.Text;
            _dbObj.SaveChanges();
            MessageBox.Show("Update Successfully....");
        }
 
Code: C#