在的String.format运行失败，整数数组 [英] string.Format fails at runtime with array of integers

问题描述

考虑的String.format（），其参数是一个字符串，其中包括在过载列表中，一个 [对象] 或多个对象。

这语句成功：

 串富=的String.Format（{0} {1}，5,6）;
 

为做到这一点：

  [对象] myObjs =新对象[] {8,9};
字符串巴兹=的String.Format（{0}和{1}，myObjs;
 

一样字符串数组：

 的String [] = myStrings新的String [] {ABC，XYZ};
字符串巴兹=的String.Format（{0} {1}，myStrings）;
 

看来，整数，当单独指定，可以盒装或胁迫键入这又是强制转换为字符串对象，

该语句将失败的运行

  INT [] = myInts新INT [] {8,9};
串吧=的String.Format（{0}和{1}，myInts）;
 

  

索引（从零开始）必须大于参数列表的大小大于或等于零且小于

• 为什么没有或不能在int数组被强制或盒装到 [对象] 或的String [] ？


• 出于好奇，一个小一点的，为什么不编译器捕获此？

解决方案

调用失败，同样的原因下面也将失败：

 串富=的String.Format（{0} {1}，5）;
 

您在格式指定两个论点，但只指定一个对象。

由于 INT [] 作为一个对象，它是该功能的完全有效的参数传递的编译器不抓住它。

另外请注意，数组协方差不值类型的工作，所以你不能做的：

  [对象] myInts = INT新[] {8,9};
 

然而，你可以逃脱：

  [对象] myInts =新的字符串[] {8，9};
串吧=的String.Format（{0} {1}，myInts）;
 

这将工作，因为你会使用一个接受对象的String.Format 超载[] 。

Consider string.Format() whose parameters are a string and, among others in the overload list, an object[] or many objects.

This statement succeeds:

string foo = string.Format("{0} {1}", 5, 6);

as does this:

object[] myObjs = new object[] {8,9};
string baz = string.Format("{0} and {1}", myObjs;

as does an array of strings:

string[] myStrings = new string[] {"abc", "xyz"};
string baz = string.Format("{0} {1}", myStrings);

It seems that the integers, when specified individually, can be boxed or coerced to type object, which in turn is coerced to a string.

This statement fails at runtime.

int[] myInts = new int[] {8,9};
string bar = string.Format("{0} and {1}", myInts);

Index (zero based) must be greater than or equal to zero and less than the size of the argument list.

• Why doesn't or can't the int array be coerced or boxed to an object[] or string[]?
• Out of a small bit of curiosity, why doesn't the compiler catch this?

解决方案

The call fails with the same reason the following will also fail:

string foo = string.Format("{0} {1}", 5);

You are specifying two arguments in the format but only specifying one object.

The compiler does not catch it because int[] is passed as an object which is a perfectly valid argument for the function.

Also note that array covariance does not work with value types so you cannot do:

object[] myInts = new int[] {8,9};

However you can get away with:

object[] myInts = new string[] { "8", "9" };
string bar = string.Format("{0} {1}", myInts);

which would work because you would be using the String.Format overload that accepts an object[].

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