Bool Methods in C#

Question

I want a WinFormApp to calculate the Prime numbers between 100 to 1000 and display them in a "lb" list box. But I'm facing with this error:

WinFormApp1.Form1.pn(int)': not all code paths return a value

bool pn(int n)
{
    for (int j = 2; j <= n; j++)
    {
        if (n % j != 0)
            return false;
        return true;
    }
}


private void button1_Click(object sender, EventArgs e)
{
    for (int i = 100; i <= 1000; i++)
    {
        if (pn(i) == true)
            lb.Items.Add(i);
    }
} 

Answer 1

bool pn(int n)
{
    for (int j = 2; j <= n; j++)
    {
        if (n % j == 0)
         {
              return false;
         }

    }
    return true;
}

Answer 2

You simply placed your return true inside the loop by mistake. As well as giving incorrect results, it the compiler can see that if the loop finishes, there'll be no value returned, hence the compile error.

bool pn(int n)
{
    for (int j = 2; j <= n; j++)
    {
        if (n % j != 0)
            return false;
    }
    return true;
}