Return False if variable isn't boolean

Question

How can I the code below to return False if usable is anything other than True (anything other than bool), currently my code throws an exception usable is not a bool.

if (!Boolean.Parse(readValue("Useable"))) return true;
return (defined.ContainsKey(key) || (key == "Useable"));

Answer 1

var result = Equals(true, myobject);

Answer 2

bool isUseable;
bool.TryParse(readValue("Useable"), out isUseable);

HTH, Kent

Answer 3

How about:

return (readValue("Useable") == "TRUE");

EDITED as a result of Drew's comment

Answer 4

bool isUseable;
if (bool.TryParse(readValue("Useable"), out isUseable))
    return isUseable;
return false;

Answer 5

This is the simplest and fastest approach:

return "True".Equals(readValue("Useable"), StringComparison.OrdinalIgnoreCase);

Note: Boolean.TryParse is not a good choice as it is significantly slower than a simple string comparison. Please see the results of this test (using Jon Skeet's BenchmarkHelper):

using System;
using BenchmarkHelper;

class Example
{
    static void Main()
    {
     var results = TestSuite.Create
                ("Boolean.TryParse vs. String comparison", "True", true)
         .Add(tryParse)
         .Add(stringComparison)
         .RunTests()
         .ScaleByBest(ScalingMode.VaryDuration);

     results.Display(ResultColumns.NameAndDuration | ResultColumns.Score,
       results.FindBest());  
    }

    static Boolean tryParse(String input)
    {
     Boolean result;
     Boolean.TryParse(input, out result);
     return result;
    }

    static Boolean stringComparison(String input)
    {
     return "True".Equals(input, StringComparison.OrdinalIgnoreCase); 
    }
}

Output:

============ Boolean.TryParse vs. String comparison ============
tryParse         12.118 6.03
stringComparison 21.895 1.00