如何检查字符串是否包含 C# 中的字符？
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How can I check if a string contains a character in C#?
提问by Samantha J T Star
Is there a function I can apply to a string that will return true of false if a string contains a character.
是否有一个函数可以应用于字符串，如果字符串包含一个字符，该函数将返回 true 或 false。
I have strings with one or more character options such as:
我有包含一个或多个字符选项的字符串，例如：
var abc = "s";
var def = "aB";
var ghi = "Sj";
What I would like to do for example is have a function that would return true or false if the above contained a lower or upper case "s".
例如，我想做的是有一个函数，如果上面包含小写或大写的“s”，则该函数将返回 true 或 false。
if (def.Somefunction("s") == true) { }
Also in C# do I need to check if something is true like this or could I just remove the "== true" ?
同样在 C# 中，我是否需要检查这样的事情是否属实，或者我可以删除“== true”吗？
采纳答案by Anders Tornblad
You can use the extension method .Contains()from the namespace System.Linq:
您可以使用.Contains()命名空间 System.Linq 中的扩展方法：
using System.Linq;
...
if (abc.ToLower().Contains('s')) { }
And no, to check if a boolean expression is true, you don't need == true
不，要检查布尔表达式是否为真，您不需要 == true
Since the Containsmethod is an extension method, my solution appeared to be confusing to some. Here are two versions that don't require you to add using System.Linq;:
由于该Contains方法是一种扩展方法，因此我的解决方案对某些人来说似乎令人困惑。以下是不需要您添加的两个版本using System.Linq;：
if (abc.ToLower().IndexOf('s') != -1) { }
// or:
if (abc.IndexOf("s", StringComparison.CurrentCultureIgnoreCase) != -1) { }
Update
更新
If you want to, you can write your own extensions method for easier reuse:
如果需要，您可以编写自己的扩展方法以便于重用：
public static class MyStringExtensions
{
public static bool ContainsAnyCaseInvariant(this string haystack, char needle)
{
return haystack.IndexOf(needle, StringComparison.InvariantCultureIgnoreCase) != -1;
}
public static bool ContainsAnyCase(this string haystack, char needle)
{
return haystack.IndexOf(needle, StringComparison.CurrentCultureIgnoreCase) != -1;
}
}
Then you can call them like this:
然后你可以这样调用它们：
if (def.ContainsAnyCaseInvariant('s')) { }
// or
if (def.ContainsAnyCase('s')) { }
In most cases when dealing with user data, you actually want to use CurrentCultureIgnoreCase(or the ContainsAnyCaseextension method), because that way you let the system handle upper/lowercase issues, which depend on the language. When dealing with computational issues, like names of HTML tags and so on, you want to use the invariant culture.
在大多数情况下，在处理用户数据时，您实际上想要使用CurrentCultureIgnoreCase(或ContainsAnyCase扩展方法)，因为这样可以让系统处理取决于语言的大写/小写问题。在处理计算问题时，例如 HTML 标签的名称等，您希望使用不变文化。
For example: In Turkish, the uppercase letter Iin lowercase is ?(without a dot), and not i(with a dot).
例如：在土耳其语中，I小写的大写字母是?（不带点），而不是i（带点）。
回答by bniwredyc
bool containsCharacter = test.IndexOf("s", StringComparison.OrdinalIgnoreCase) >= 0;
回答by tobias86
The following should work:
以下应该工作：
var abc = "sAb";
bool exists = abc.IndexOf("ab", StringComparison.CurrentCultureIgnoreCase) > -1;
回答by Shamim Hafiz
回答by Rich O'Kelly
You can use the IndexOfmethod, which has a suitable overload for string comparison types:
您可以使用该IndexOf方法，该方法具有适合字符串比较类型的重载：
if (def.IndexOf("s", StringComparison.OrdinalIgnoreCase) >= 0) ...
Also, you would not need the == true, since an if statement only expects an expression that evaluates to a bool.
此外，您不需要== true，因为 if 语句只需要一个计算结果为 a 的表达式bool。
回答by Sergejs
It will be hard to work in C# without knowing how to work with strings and booleans. But anyway:
如果不知道如何使用字符串和布尔值，就很难在 C# 中工作。但无论如何：
String str = "ABC";
if (str.Contains('A'))
{
//...
}
if (str.Contains("AB"))
{
//...
}
回答by Karan Shah
here is an example what most of have done
这是大多数人所做的一个例子
using System;
class Program
{
static void Main()
{
Test("Dot Net Perls");
Test("dot net perls");
}
static void Test(string input)
{
Console.Write("--- ");
Console.Write(input);
Console.WriteLine(" ---");
//
// See if the string contains 'Net'
//
bool contains = input.Contains("Net");
//
// Write the result
//
Console.Write("Contains 'Net': ");
Console.WriteLine(contains);
//
// See if the string contains 'perls' lowercase
//
if (input.Contains("perls"))
{
Console.WriteLine("Contains 'perls'");
}
//
// See if the string contains 'Dot'
//
if (!input.Contains("Dot"))
{
Console.WriteLine("Doesn't Contain 'Dot'");
}
}
}
回答by Aphelion
You can create your own extention method if you plan to use this a lot.
如果您打算经常使用它，您可以创建自己的扩展方法。
public static class StringExt
{
public static bool ContainsInvariant(this string sourceString, string filter)
{
return sourceString.ToLowerInvariant().Contains(filter);
}
}
example usage:
用法示例：
public class test
{
public bool Foo()
{
const string def = "aB";
return def.ContainsInvariant("s");
}
}
