Question

I have a text file with a certain format. First comes an identifier followed by three spaces and a colon. Then comes the value for this identifier.

ID1   :Value1  
ID2   :Value2  
ID3   :Value3

What I need to do is searching e.g. for ID2 : and replace Value2 with a new value NewValue2. What would be a way to do this? The files I need to parse won’t get very large. The largest will be around 150 lines.

Answer 1

If the file isn’t that big you can do a File.ReadAllLines to get a collection of all the lines and then replace the line you’re looking for like this

using System.IO;
using System.Linq;
using System.Collections.Generic;

List<string> lines = new List<string>(File.ReadAllLines("file"));
int lineIndex = lines.FindIndex(line => line.StartsWith("ID2   :"));
if (lineIndex != -1)
{
    lines[lineIndex] = "ID2   :NewValue2";
    File.WriteAllLines("file", lines);
}