Convert `bool`, `int`

A bool can be converted to 0 or 1. In other languages, false is equivalent to 0 and true is equivalent to 1. This is not possible in the C# language.

Conversion notes

We convert bools to ints, first running through an example. We then test unsafe code in converting bools to ints. We benchmark to ensure our method is fast.

An example

We cannot implicitly convert from bool to int. The C# compiler uses this rule to enforce program correctness. The same rule mandates you cannot test an int in an if-statement.

Note When you try to convert a bool into an int with an implicit cast, you receive an error: "Can not convert type bool to int."

Version 1 This version of the code uses a ternary expression to convert a bool into an int (1 or 0).

Version 2 Here we use the Convert.ToIn32 method to convert the bool to an int—no ternary is required.

Info Opening up Convert.ToInt32 up in IL Disassembler, I found it performs the same logic as the ternary (it branches).

using System;

// Version 1: convert bool to int.
bool testBool = true;
int testInt = testBool ? 1 : 0;

Console.WriteLine("TEST BOOL: " + testBool);
Console.WriteLine("TEST INT: " + testInt);

// Version 2: also convert bool to int.
bool testBool2 = false;
int testInt2 = Convert.ToInt32(testBool2);
Console.WriteLine("TEST BOOL 2: " + testBool2);
Console.WriteLine("TEST INT 2: " + testInt2);TEST BOOL: True
TEST INT: 1
TEST BOOL 2: False
TEST INT 2: 0

A benchmark

I benchmarked the 2 statements and found identical performance. The compiler efficiently inlines Convert.ToInt32 to be the same as the ternary expression.

Version 1 Here we use the ternary expression to convert the bool to an int (either 0 or 1).

Version 2 This code uses the Convert.ToIn32 method to convert the bool to an int. Its results are identical.

Result The performance of the 2 versions is the same—use whichever version seems clearest.

using System;
using System.Diagnostics;

const int _max = 100000000;
var s1 = Stopwatch.StartNew();
// Version 1: use ternary.
for (int i = 0; i < _max; i++)
{
    bool testBool = true;
    int testInt = testBool ? 1 : 0;
    if (testInt != 1)
    {
        return;
    }
}
s1.Stop();
var s2 = Stopwatch.StartNew();
// Version 2: use Convert.ToInt32.
for (int i = 0; i < _max; i++)
{
    bool testBool = true;
    int testInt = Convert.ToInt32(testBool);
    if (testInt != 1)
    {
        return;
    }
}
s2.Stop();
Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));0.27 ns    Use ternary
0.27 ns    Use Convert.ToInt32

Other approaches

There are other ways to convert bools to ints, including unsafe code with casts, and StructLayout-based approaches. These tend to be slower, and not worth the trouble.

A summary