Convert Dictionary, string

A C# Dictionary can be converted to string format. This string can then be persisted in a text file and read back into memory.

Notes, round trip

With 2 methods, we can round-trip the Dictionary and string. A method like GetDict() can be used in many places in a program.

An example

We write the values of Dictionary types to the disk and then parse them. I had to store a Dictionary of string keys and int values. This is also called serialization.

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

class Program
{
    static void Main()
    {
        var data = new Dictionary<string, int>()
        {
            { "salmon", 5 },
            { "tuna", 6 },
            { "clam", 2 },
            { "asparagus", 3 }
        };

        // Step 1: get string from Dictionary.
        string value = GetLine(data);

        // Step 3: save to disk.
        File.WriteAllText("dict.txt", value);

        // Step 4: get dictionary again.
        var result = GetDict("dict.txt");
        foreach (var pair in result)
        {
            Console.WriteLine("PAIR: " + pair);
        }
    }

    static string GetLine(Dictionary<string, int> data)
    {
        // Step 2: build up the string data.
        StringBuilder builder = new StringBuilder();
        foreach (var pair in data)
        {
            builder.Append(pair.Key).Append( ":").Append(pair.Value).Append(',');
        }
        string result = builder.ToString();
        // Remove the end comma.
        result = result.TrimEnd(',');
        return result;
    }

    static Dictionary<string, int> GetDict(string file)
    {
        // Step 5: parse in the dictionary from a string.
        var result = new Dictionary<string, int>();
        string value = File.ReadAllText(file);
        // Split the string.
        string[] tokens = value.Split(new char[] { ':', ',' }, StringSplitOptions.RemoveEmptyEntries);
        // Build up our dictionary from the string.
        for (int i = 0; i < tokens.Length; i += 2)
        {
            string name = tokens[i];
            string freq = tokens[i + 1];

            // Parse the int.
            int count = int.Parse(freq);
            // Add the value to our dictionary.
            result[name] = count;
        }
        return result;
    }
}
PAIR: [salmon, 5]
PAIR: [tuna, 6]
PAIR: [clam, 2]
PAIR: [asparagus, 3]

Exceptions

Whenever you deal with the file system, your input may become corrupted. If your code is not critical, it is worthwhile to try to recover from any errors.

Summary

We persisted the Dictionary to the disk and read it back in from the file. You can sometimes develop custom methods to do this with the best performance.