在 C# 中将整数添加到字符串 [英] Adding integers to strings in C#

问题描述

最近我被告知可以将整数(和其他类型)连接到字符串，反之亦然，即

Recently I have been informed that it is possible to concatenate integers (and other types) to string and vice versa, i.e.

// x == "1234"
// y == "7890"
string x = "123" + 4;
string y = 7 + "890";

出于某种原因，我认为这种事情是不被允许的，所以我一直使用(从 .NET 2 开始)这种形式:

For some reason I didn't think this kind of thing was allowed, so I have always been using (since .NET 2) the form:

// x == "1234"
// y == "7890"
string x = "123" + 4.ToString();
string y = 7.ToString() + "890";

其中整数被转换为字符串.以前的版本一直可用吗，我错过了，还是 C# 4 的新版本(我现在正在使用)?

where the integers are converted to strings. Has the former version always been available, and I've missed it, or is it something that is new to C# 4 (which is what I am using now)?

推荐答案

这一直存在.如果至少一个操作数是字符串，则 + 等效于 string.Concat().string.Concat() 有一个采用 object 实例的重载.在内部，它会在连接之前调用对象的 ToString() 方法.

This has always been there. The + is equivalent to string.Concat() if at least one of the operands is a string. string.Concat() has an overload that takes an object instance. Internally it will call the object's ToString() method before concatenating.

在 C# 规范中找到相关部分 - 第 7.7.4 节加法运算符:

Found the relevant section in the C# spec - section 7.7.4 Addition operator:

字符串连接:

string operator +(string x, string y);
string operator +(string x, object y);
string operator +(object x, string y);

二元 + 运算符在其中一个或两个时执行字符串连接操作数是字符串类型.如果字符串连接的操作数是null，一个空字符串被替换.否则，任何非字符串参数通过调用从类型对象继承的虚拟 ToString 方法.如果 ToString返回 null，一个空字符串被替换.

The binary + operator performs string concatenation when one or both operands are of type string. If an operand of string concatenation is null, an empty string is substituted. Otherwise, any non-string argument is converted to its string representation by invoking the virtual ToString method inherited from type object. If ToString returns null, an empty string is substituted.

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