无法隐式转换类型'诠释'到'炭'，而使用聚合扩展方法 [英] Cannot implicitly convert type 'int' to 'char' while using Aggregate Extension method

问题描述

试图扭转一个字符串，但在聚合函数得到错误

Trying to reverse a string but getting error in Aggregate function

private string Reverse(string strValue)
        {

            char[] chArray = strValue.ToCharArray();
            var reverse = chArray.Reverse();

            var res = reverse.Aggregate((a,b)=>a+b);

            return res.ToString();
        }

无法隐式转换类型'诠释'到'字符。一个显式转换存在（是否缺少强制转换？）
那么，什么是错？

Cannot implicitly convert type 'int' to 'char'. An explicit conversion exists (are you missing a cast?) So what is the mistake?

推荐答案

正是因为它说：结果 A + b 是 INT ，但你希望它是一个字符。为了得到它的编译的你可以使用：

Exactly as it says: the result of a + b is an int, but you want it to be a char. To get it to compile you can just use:

var res = reverse.Aggregate((a,b)=>(char) (a+b));

...但我不认为这会做你想要什么。

... but I don't think that will do what you want it to.

我建议你不要使用LINQ此入手：

I suggest you don't use LINQ for this to start with:

private string Reverse(string strValue)
{
    char[] chArray = strValue.ToCharArray();
    Array.Reverse(chArray);
    return new string(chArray);
}

请注意，这的不的正常的工作。之类的东西组合字符，代理对等

Note that this doesn't work properly with things like combining characters, surrogate pairs etc.

如果你真的想使用LINQ，可以用做：

If you really wanted to use LINQ, you could do it with:

private string Reverse(string strValue)
{
    return new string(strValue.Reverse().ToArray());
}

有没有必要打电话总结。如果你的真正的想让它慢和使用字符串连接与总结（这将是为O（n ² ）），你可以做这样的：

There's no need to call Aggregate. If you really want to make it slow and use string concatenation with Aggregate (it'll be O(n²)) you can do it like this:

private string Reverse(string strValue)
{
    return strValue.Reverse().Aggregate("", (str, c) => str + c);
}

下面是我们所提供的字符串种子值，所以该参数 STR 将是一个字符串， + 将字符串连接，而不是人物的除了的

Here's we've provided a string seed value, so the parameter str will be a string and + will be string concatenation, not character addition.

您可以使其使用更高效的的StringBuilder ：

You can make it more efficient using StringBuilder:

private string Reverse(string strValue)
{
    return strValue.Reverse()
                   .Aggregate(new StringBuilder(), (sb, c) => sb.Append(c))
                   .ToString();
}

...但我仍然不知道它是值得的......

... but I'm still not sure it's worth it...

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