*I have this Code but it is not working :*

```
double N1 = int.Parse(TB_S1.Text);
double N2 = int.Parse(TB_S2.Text);
double N3 = int.Parse(TB_S3.Text);
double N4 = int.Parse(TB_P1Y.Text);
double N5 = int.Parse(TB_P2X.Text);

double N11 = N1 + N2;
double N6 = N2 + N3;
double N7 = N3 + N4;

double R;

if ((N11 = N6 = N7))
{
    messageBox.Show("Corect");
}

```

Edit: 
solution: th eproblem was using single = instead of ==