Since every object in C# derives from System.Object, it’s possible to “cheat” type safety by using the object type and casting objects to the desired type at run-time.
For example, assume we have a method that adds two parameters that are assumed to be numbers:
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| public static double AddNums(object n1, object n2){ double d1 = Convert.ToDouble(n1); double d2 = Convert.ToDouble(n2); return d1 + d2;} |
This is convenient because now we can pass in any numeric type we like because we can implicitly cast anything toobject.
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| int i1 = 5, i2 = 7;double d1 = 10.2, d2 = 23.2;// These all work as expecteddouble sum = AddNums(i1, i2);sum = AddNums(d1, d2);sum = AddNums(i1, d1); |
The problem is that the compiler won’t complain if we try to pass in some non-numeric object. The following code will compile fine, but throw an exception at run-time.
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| string s = "Uh-oh";sum = AddNums(s, 1); |