将空数组作为可选参数的默认值传递

如何定义一个默认使用空数组的可选数组的函数？

public void DoSomething(int index, ushort[] array = new ushort[] {},
bool thirdParam = true)

结果:

“ array”的默认参数值必须是编译时常数。

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最佳答案

You can't create compile-time constants of object references.

The only valid compile-time constant you can use is null, so change your code to this:

public void DoSomething(int index, ushort[] array = null,
bool thirdParam = true)

And inside your method do this:

array = array ?? new ushort[0];

(from comments) From C# 8 onwards you can also use the shorter syntax:

array ??= new ushort[0];

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If you can make the array the last argument you could also do this:

public void DoSomething(int index, bool wasThirdParam = true, params ushort[] array)

The compiler will automatically pass an empty array if it is not specified, and you get the added flexibility to either pass an array as a single argument or put the elements directly as variable length arguments to your method.

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I know it's an old question, and whilst this answer doesn't directly solve how to get around the limitations imposed by the compiler, method overloading is an alternative:

   public void DoSomething(int index, bool thirdParam = true){
DoSomething(index, new ushort[] {}, thirdParam);
}


public void DoSomething(int index, ushort[] array, bool thirdParam = true){


...
}