Question

Assume that I have these two overloaded functions.

public static void Main(string[]args)
{
     int x=3;
     fn(x); 
}

static void fn(double x)
{ 
    Console.WriteLine("Double");
}

static void fn(float x)
{
    Console.WriteLine("Float");
}

Why will the compiler choose the float function?

Answer 1

It follows the rules of section 7.5.3.2 of the C# 4 spec.

int is implicitly convertible to both float and double, so both candidate methods are applicable. However, the conversion from int to float is “better than” the conversion from int to double according to section 7.5.3.2-7.5.3.5:

Given two different types T1 and T2, T1 is a better conversion target than T2 if at least one of the following holds:

• An implicit conversion from T1 to T2 exists, and no implicit conversion from T2 to T1 exists
• … [irrelevant in this case]

Here, there’s an implicit conversion from float to double, but no implicit conversion from double to float – so float is a better conversion target than double.