使用此代码，这可能对您有帮助

use this code , this may helps you

//Read all lines from the file
string[] data=File.ReadAllLines("myfile.txt");
//replace the first line with your data.
 data[0] = "my own text";
//write all data again into the file.
 File.WriteAllLines("myfileout.txt", data);

谢谢
--RA

Thanks
--RA

string[] lines = File.ReadAllLines("file.txt");

lines[0]="New Line to overwrite";

File.WriteAllLines("file.txt", lines );