我已经看到一些程序员使用＆安培; 和 + 字符串处理。

I have seen several programmers use & and + for string manipulation.

如：

dim firstvar as string
dim secondvar as string
dim thirdvar as string

thirdvar = firstvar & secondvar

或者是：

thirdvar = firstvar + secondvar

什么关系呢？如果是这样，为什么？

Does it matter? If so, why?

推荐答案

在 + 和 ＆安培; 运营商的没有的相同的VB.NET。

The + and & operators are not identical in VB.NET.

使用＆安培; 运算符表示你的意图来连接字符串，而 + 运算符表示你的意图添加数字。使用＆安培; 运营商将经营两侧转换成字符串。当已经混合类型（的前pression一侧是一个字符串，另一种是一个数字），您的操作者的使用将确定结果。

Using the & operator indicates your intention to concatenate strings, while the + operator indicates your intention to add numbers. Using the & operator will convert both sides of the operation into strings. When you have mixed types (one side of the expression is a string, the other is a number), your usage of the operator will determine the result.

1 + "2" = 3 'This will cause a compiler error if Option Strict is on'
1 & "2" = "12"
1 & 2 = "12"
"text" + 2 'Throws an InvalidCastException since "text" cannot be converted to a Double'

所以，我的准则（除了避免混合类型那样）是使用＆安培; 连接字符串的时候，只是为了确保你的意图是明确的编译器，避免无法找到的使用 + 运算符连接涉及到的bug。

So, my guideline (aside from avoiding mixing types like that) is to use the & when concatenating strings, just to make sure your intentions are clear to the compiler, and avoid impossible-to-find bugs involving using the + operator to concatenate.