How to get all files inside folder using C# easily?

You can simply use the "DirectoryInfo" class, and the ".GetFiles" method, as shown in below code

DirectoryInfo dir = new DirectoryInfo(@"E:\YourFolderName");
FileInfo[] AllTxtFiles= dir.GetFiles("*.txt"); //Getting only Text files

foreach(var fle in AllTextFiles)
{
   //read files content or do something
}

OR

You can simply use

foreach (string file in Directory.EnumerateFiles(folderPath, "*.txt"))
{
       //read content
    string contents = File.ReadAllText(file);
}

For both of the above solutions, you will have to use namespace "System.IO".