在C＃中，检查stringbuilder是否包含子字符串的最佳方法 [英] In C#, best way to check if stringbuilder contains a substring

问题描述

我有一个现有的 StringBuilder 对象，代码向其附加了一些值和定界符。

I have an existing StringBuilder object, the code appends some values and a delimiter to it.

I想要修改代码以添加逻辑，即在添加文本之前，它将检查 StringBuilder 中是否已经存在。如果没有，则仅会附加文本，否则它将被忽略。

I want to modify the code to add the logic that before appending the text, it will check if it already exists in the StringBuilder. If it does not, only then will it append the text, otherwise it is ignored.

这样做的最佳方法是什么？我是否需要将对象更改为 string 类型？我需要一种不会影响性能的最佳方法。

What is the best way to do so? Do I need to change the object to string type? I need the best approach that will not hamper performance.

public static string BuildUniqueIDList(context RequestContext)
{
    string rtnvalue = string.Empty;
    try
    {
        StringBuilder strUIDList = new StringBuilder(100);
        for (int iCntr = 0; iCntr < RequestContext.accounts.Length; iCntr++)
        {
            if (iCntr > 0)
            {
                strUIDList.Append(",");
            }

            // need to do somthing like:
            // strUIDList.Contains(RequestContext.accounts[iCntr].uniqueid) then continue
            // otherwise append
            strUIDList.Append(RequestContext.accounts[iCntr].uniqueid);
        }
        rtnvalue = strUIDList.ToString();
    }
    catch (Exception e)
    {
        throw;
    }
    return rtnvalue;
}

我不确定拥有这样的东西是否会有效：

I am not sure if having something like this will be efficient:

if (!strUIDList.ToString().Contains(RequestContext.accounts[iCntr].uniqueid.ToString()))

推荐答案

我个人会使用：

return string.Join(",", RequestContext.accounts
                                      .Select(x => x.uniqueid)
                                      .Distinct());

无需显式循环，手动使用 StringBuilder 等...只是声明式地表达所有内容：）

No need to loop explicitly, manually use a StringBuilder etc... just express it all declaratively :)

（您需要调用 ToArray（）最后，如果您不使用.NET 4，这显然会降低效率...但是我怀疑它会成为您应用程序的瓶颈。）

(You'd need to call ToArray() at the end if you're not using .NET 4, which would obviously reduce the efficiency somewhat... but I doubt it'll become a bottleneck for your app.)

编辑：好吧，对于非LINQ解决方案...如果大小是合理小，我只想这样做：

Okay, for a non-LINQ solution... if the size is reasonably small I'd just for for:

// First create a list of unique elements
List<string> ids = new List<string>();
foreach (var account in RequestContext.accounts)
{
    string id = account.uniqueid;
    if (ids.Contains(id))
    {
        ids.Add(id);
    }
}

// Then convert it into a string.
// You could use string.Join(",", ids.ToArray()) here instead.
StringBuilder builder = new StringBuilder();
foreach (string id in ids)
{
    builder.Append(id);
    builder.Append(",");
}
if (builder.Length > 0)
{
    builder.Length--; // Chop off the trailing comma
}
return builder.ToString();

如果可以有 large 个字符串集合，则可以使用 Dictionary< string，string> 作为一种伪造的 HashSet< string> 。

If you could have a large collection of strings, you might use Dictionary<string, string> as a sort of fake HashSet<string>.

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