感谢马克·格拉维尔和奥利维尔·罗吉尔。
答案是使用管道。
我的控制台应用程序main.cs

Public static void main(args){
     String input = Console.ReadLine();
     Console.WriteLine(input);
}

输入. txt文件

Hello world

命令行

myconsoleapp.exe < input.txt

输出

Hello world

参考：ss64.com/nt/syntax-redirection.html

How-to: Redirection
   command > filename        Redirect command output to a file

   command >> filename       APPEND into a file

   command < filename        Type a text file and pass the text to command

   commandA  |  commandB     Pipe the output from commandA into commandB

   commandA &  commandB      Run commandA and then run commandB
   commandA && commandB      Run commandA, if it succeeds then run commandB
   commandA || commandB      Run commandA, if it fails then run commandB

   commandA && commandB || commandC
                             If commandA succeeds run commandB, if commandA fails run commandC
                             ( Note that if commandB fails, that will also trigger running commandC )

您可以使用Console.SetIn()方法将控制台的流转换为文本文件，这样您将直接使用Console.ReadLine()从filename.txt中读取。

文件名.txt〉〉你好，世界

TextReader inp = File.OpenText(path: @"FullPath\filename.txt");
Console.SetIn(inp);
string s = Console.ReadLine();
Console.WriteLine(s);

**输出：**Hello World