如何使用C＃从下面的字符串中提取键

Question

输入查询

 select * from mytable where projectname = __$ProjectName$__ and  projectid = __$ProjectId$__ and env = __$EnvType$__

我希望在下面的输出中显示字符串（List<string>）的列表。（双下划线+美元+“字符串” +美元+双下划线） 语言：C＃

 __ $ProjectName$__
 __ $ProjectId$__
 __ $EnvType$__

Answer 1

使用Linq：

List<string> output = input.Split(' ').Where(x => x.StartsWith("__$") && x.EndsWith("$__")).ToList();

Answer 2

尝试正则表达式；如果键

1. 从__$开始
2. 包含 标识符（以字母A..Z，a..z开头，可以包含字母或\和数字A..Z，{ {1}}，a..z）
3. 以0..9
结尾

要匹配的模式是$__

代码：

__\$[A-Za-z]+[A-Za-z0-9]*\$__

结果：

using System.Text.RegularExpressions;

...

string source = 
  "select * from mytable where projectname = __$ProjectName$__ and  projectid = __$ProjectId$__ and env = __$EnvType$__";

List<string> keys = Regex
  .Matches(source, @"__\$[A-Za-z]+[A-Za-z0-9]*\$__")
  .OfType<Match>()
  .Select(match => match.Value)
  .ToList();

Console.Write(string.Join(Environment.NewLine, keys));

Answer 3

using System;
using System.Linq;
using System.Text.RegularExpressions;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var expression = @"select * from mytable where projectname = __$ProjectName$__ and  projectid = __$ProjectId$__ and env = __$EnvType$__";

            var output = new Regex(@"__\$[^\s]+?\$__")
                .Matches(expression)
                .Cast<Match>()
                .Select(m => m.Value)
                .ToList();

            output.ForEach(Console.WriteLine);
        }
    }
}