C# Cookbook

3.3. Converting a String Representation of an Object into an Actual Object

Problem

You need a way of accepting a string containing a textual representation of an object and converting it to an object usable by your application. For example, if you were provided with the string representation of a line (x1, y1)(x2, y2), you would want to convert it into a Line structure.

Solution

Implement a Parse method on your Line structure:

using System;
using System.Text;
using System.Text.RegularExpressions;

public struct Line
{
    public Line(int startX, int startY, int endX, int endY)
    {
        x1 = startX;
        x2 = endX;
        y1 = startY;
        y2 = endY;
    }

    public int x1;
    public int y1;
    public int x2;
    public int y2;

    public static Line Parse(string stringLine)
    {
        if (stringLine == null)
        {
            throw (new ArgumentNullException("stringLine", 
                       "A null cannot be passed into the Parse method."));
        }

        // Take this string (x1,y1)(x2,y2) and convert it to a Line object
        int X1 = 0;
        int Y1 = 0;
        int X2 = 0;
        int Y2 = 0;

        MatchCollection MC = Regex.Matches(stringLine, 
                @"\s*\(\s*(?<x1>\d+)\s*\,\s*(?<y1>\d+)\s*\)\s*
                     \(\s*(?<x2>\d+)\s*\,\s*(?<y2>\d+)\s*\)" );

        if (MC.Count == 1)
        {
            Match M = MC[0];
            X1 = int.Parse(M.Groups["x1"].Value);
            Y1 = int.Parse(M.Groups["y1"].Value);
            X2 = int.Parse(M.Groups["x2"].Value);
            Y2 = int.Parse(M.Groups["y2"].Value);
        }
        else
        {
            throw (new ArgumentException(
              "The value " + stringLine + " is not a well formed Line value."));
        }

        return (new Line(X1, Y1, X2, Y2));
    }
}

Discussion

The Parse method is used to reconstruct ...