C# does not work well with boxed numerical values. Unlike Visual Basic, the basic numeric comparison operators such as == do not work with boxed types even when both values are the same type.
| Variable | Type | Value |
|---|---|---|
| a | int | 0 |
| b | decimal | 0.0 |
| c | decimal | 0.0 |
| boxA | boxed int | 0 |
| boxB | boxed decimal | 0.0 |
| boxC | boxed decimal | 0.0 |
| dynA | dynamic holding an int | 0 |
| dynB | dynamic holding a decimal | 0.0 |
| dynC | dynamic holding a decimal | 0.0 |
| Comparison | C# | VB |
|---|---|---|
| a==b | true | true |
| b==a | true | true |
| b==c | true | true |
| a.Equals(b) | false | <-- |
| b.Equals(c) | true | <-- |
| boxA == boxB | false | true |
| boxB == boxA | false | true |
| boxB == boxC | false | true |
| boxA.Equals(boxB) | false | <-- |
| boxB.Equals(boxC) | true | <-- |
| dynA == dynB | true | n/a |
| dynB == dynA | true | n/a |
| dynB == dynC | true | n/a |
As you can see, using C# 3 and earlier even two boxed decimals with the same value will evaluate as being unequal. This occurs even when the Equals method on the Decimal class would otherwise return true.
Fortunately with C# 4 you can avoid these problems. By first casting the boxed values as dynamic, you do get the correct results even when comparing different types.
Console.WriteLine((dynamic)boxA == (dynamic)boxB);
