Convert Dictionary to String (Write to File)Transform a Dictionary into a string with StringBuilder, and get a Dictionary from a string again.
This page was last reviewed on Dec 10, 2021.
Convert Dictionary, string. A Dictionary can be converted to string format. This string can then be persisted in a text file and read back into memory.
Dictionary Binary File
Shows a string dictionary
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.
Detail The GetLine method receives a Dictionary that was declared at class-level. It uses a StringBuilder.
Next GetLine() iterates through the Dictionary's KeyValuePair collection. It appends the data to a StringBuilder.
Detail Next, we must get a new Dictionary from the file we saved it to. GetDict here does that for us.
Detail The string has commas and semicolons as separators. We split on these and consume 2 results in each loop iteration.
Shows a string dictionary
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} }; // Get string from Dictionary. string value = GetLine(data); // Save to disk. File.WriteAllText("C:\\programs\\dict.txt", value); // Get dictionary again. var result = GetDict("C:\\programs\\dict.txt"); foreach (var pair in result) { Console.WriteLine("PAIR: " + pair); } } static string GetLine(Dictionary<string, int> data) { // 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) { 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. if (result.ContainsKey(name)) { result[name] += count; } else { result.Add(name, count); } } return result; } }
Exceptions. Whenever you deal with the file system, your input may become corrupted. Whenever you deal with the file system and your code is not critical, try to recover from any errors.
A 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.
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Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Dec 10, 2021 (image).
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