Question

How to check if line containing a specific string exist in text file with Linq in C#

Answer 1

using System;
using System.IO;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool exist = (from line in File.ReadAllLines("d:\\test.txt")
                          where line == "Text File Line three"
                          select line).Count() > 0;

            if (exist)
                Console.WriteLine("Exist"); // Exist
            else
                Console.WriteLine("NOT Exist"); 
        }
    }
}

/*
run:
   
Exist
 
*/

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Answer 2

using System;
using System.IO;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool exist = (from line in File.ReadAllLines("d:\\test.txt")
                          where line == "one"
                          select line).Count() > 0;

            if (exist)
                Console.WriteLine("Exist"); 
            else
                Console.WriteLine("NOT Exist"); // NOT Exist
        }
    }
}

/*
run:
   
NOT Exist
 
*/

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Answer 3

using System;
using System.IO;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool exist = (from line in File.ReadAllLines("d:\\test.txt")
                          where line.Contains("one") // LIKE '%text%'
                          select line).Count() > 0;

            if (exist)
                Console.WriteLine("Exist"); // Exist
            else
                Console.WriteLine("NOT Exist"); 
        }
    }
}

/*
run:
   
Exist
 
*/

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Answer 4

using System;
using System.IO;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool exist = (from line in File.ReadAllLines("d:\\test.txt")
                          where line.StartsWith("Text") // LIKE 'text%' // case sensitive
                          select line).Count() > 0;

            if (exist)
                Console.WriteLine("Exist"); // Exist
            else
                Console.WriteLine("NOT Exist"); 
        }
    }
}

/*
run:
   
Exist
 
*/

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Answer 5

using System;
using System.IO;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            bool exist = (from line in File.ReadAllLines("d:\\test.txt")
                          where line.EndsWith("three") // LIKE '%text'
                          select line).Count() > 0;

            if (exist)
                Console.WriteLine("Exist"); // Exist
            else
                Console.WriteLine("NOT Exist"); 
        }
    }
}

/*
run:
   
Exist
 
*/

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