why int.TryParse cannot initialise multiple variables

Question

I am using int.TryParse to parse to variables (saved as strings in the database) and am curious why I cannot initialise 2 variables:

int min, 
    max;

using the following conditional statement:

bool lengthCompatible = int.TryParse(string1, out min) &&
                        int.TryParse(string2, out max);

Visual Studio (2015) produces the following code highlighting:

Use of unassigned local variable 'max'

Local variable 'max' might not be initialized before accessing

However, if I use 2 conditional statements:

bool minParse = int.TryParse(sentenceType.MinimumLength, out min);
bool maxParse = int.TryParse(sentenceType.MaximumLength, out max);

I can compile with no errors.

Curiouser and curiouser! Any insight appreciated.

Cheers

Answer 1

Well you're using &&, which is short-circuiting... if int.TryParse(string1, out min) returns false, the second call to int.TryParse won't be made, so max isn't definitely assigned.

You could write:

if (int.TryParse(string1, out min) &&
    int.TryParse(string2, out max))
{
    // Use min and max here
}

... because then the compiler knows that you only reach the body of the if statement if both calls have been executed.

Alternatively you could use the non-short-circuiting version with & instead of &&:

bool lengthCompatible = int.TryParse(string1, out min) &
                        int.TryParse(string2, out max);

That's slightly unusual though. The advantage of the if version above is that you'll retain the performance benefit of &&, in that you won't bother trying to parse string2 if you don't need to. (It depends on exactly what you're trying to do, of course.)