Code Inspection: Convert delegate variable to local function
Local functions, unlike lambdas or delegates, do not cause additional overhead because they are essentially regular methods. For example, instantiating and invoking a delegate requires additional members being generated by compiler and causing some memory overhead. Another benefit of local functions is their support for all the syntax elements allowed in regular methods. If it is possible to replace a delegate with local function, ReSharper suggests doing so.
Consider an example with a user-defined delegate. ReSharper replaces the delegate variable mymethod
with a local function Mymethod
. After the replacement, it also suggests removing the unused delegate MethodDelegate
.
Suboptimal code | After the quick-fix |
---|---|
class DelegateTest
{
private delegate void MethodDelegate(string message);
public static void Main(string[] args)
{
MethodDelegate mymethod = delegate(string message)
{
Console.WriteLine(message);
};
mymethod("test");
Console.ReadLine();
}
}
|
class DelegateTest
{
public static void Main(string[] args)
{
void Mymethod(string message)
{
Console.WriteLine(message);
}
Mymethod("test");
Console.ReadLine();
}
}
|
In another example, ReSharper replaces a generic delegate Func
with a local function:
Suboptimal code | After the quick-fix |
---|---|
class ConvertToLambda
{
public static int ConvertTest()
{
Func<int, int, int> sum = delegate(int x, int y)
{
return x + y;
};
return sum(10, 20);
}
}
|
class ConvertToLambda
{
public static int ConvertTest()
{
int Sum(int x, int y)
{
return x + y;
}
return Sum(10, 20);
}
}
|