I found out that in C# a+=1 is not equal to a = a+1.
For example, the following code compiles without any error: byte b = 10; b += 5;
while the following code has a compilation error: byte b = 10; b = b + 5;
Can somebody let me know why?
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The error message is always helpful – Shiplu Mokaddim Mar 23 '12 at 04:43
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The error message is: "Cannot implicitly convert type 'int' to 'byte'. An explicit conversion exists (are you missing a cast?)" – Morteza Mar 23 '12 at 04:47
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See: http://stackoverflow.com/questions/4343624/integer-summing-blues-short-short-problem – Anthony Pegram Mar 23 '12 at 04:47
3 Answers
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Because b + 5 becomes an integer ( Int32) ( mainly because there is possibility of overload)
And the compound assignment specification states below:
Otherwise, if the selected operator is a predefined operator, if the return type of the selected operator is explicitly convertible to the type of x, and if y is implicitly convertible to the type of x or the operator is a shift operator, then the operation is evaluated as x = (T)(x op y), where T is the type of x, except that x is evaluated only once.
manojlds
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Because b += 5 is compiled as if it read b = (byte)(b + 5). The cast takes care of the conversion to the proper type, so there is no error.
Ernest Friedman-Hill
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The compiler is probably treating the 5 as an Int32 in the second one. You'll need to cast it
joshuahealy
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