157 recommendations for writing high-quality code to improve C # programs--Recommendation 35: Use default to specify initial values for generic type variables

Recommendation 35: Use default to specify an initial value for a generic type variable

Some algorithms, such as the Find algorithm for generic collection list<t>, may be looking for a value type, or possibly a reference type. Within this algorithm, we often specify default values for these value types or reference type variables. So the problem is that the default initial value of a value type variable is a value of 0, whereas the default initial value of a reference type variable is a null value, which obviously causes the following compilation error:

         Public T func<t>()        {            null; return t;        }

Cannot convert null to type parameter ' T ' because it may be a non-nullable value type. Consider using "Default (T)" instead.

         Public T func<t>()        {            0;             return t;        }

The type "int" cannot be implicitly converted to "T".

So the above code should read:

         Public T func<t>()        {            default(t);             return t;        }

Thus, if it encounters t as an integer at run time, the runtime assigns it a value of 0, and if T is a reference type such as a person at run time, it will be assigned a null value.

List<t> 's Find method source code is:

[__dynamicallyinvokable] PublicT Find (predicate<t>match) {    if(Match = =NULL) {throwhelper.throwargumentnullexception (exceptionargument.match); }     for(inti =0; I < This. _size; i++)    {        if(Match ( This. _items[i])) {            return  This. _items[i]; }    }    return default(T);}

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157 recommendations for writing high-quality code to improve C # programs--Recommendation 35: Use default to specify initial values for generic type variables