How to deserialize a x-www-form-urlencoded encoded string in .NET Core 3.1 or .NET Standard?

Question

How to deserialize a x-www-form-urlencoded encoded string in .NET Core 3.1 or in .NET Standard (C#)?

I'm aware of this question - answer. However, FormDataCollection does not appear to be available in .NET Core 3.1. See here.

EDIT: I am being passed this encoded data back by another external system. I am not writing a ASP.NET Core Website/API.

Answer 1

I did some digging through the .NET source code to figure out how ASP.NET Core is parsing x-form-urlencoded data internally. It is using the FormPipeReader class which accepts a PipeReader containing the encoded data. A PipeReader can be created from a Stream which in turn can be created from a string.

var data = "foo=bar&baz=qux";
var stream = new MemoryStream(Encoding.UTF8.GetBytes(data));
var reader = new FormPipeReader(PipeReader.Create(stream));
var pairs = await reader.ReadFormAsync();
Assert.Equal("bar", pairs["foo"]);
Assert.Equal("qux", pairs["baz"]);

Answer 2

So I never found a neat answer to this question. So I banged out my own rough serializer. Posting here in case anyone gets any use from it. I still welcome a better answer! :-)

using System;
using System.Net.Http;
using System.Threading.Tasks;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Reflection;

public static class FormUrlEncodedSerializer
{
    public static async Task<string> SerializeAsync(object obj)
    {
        if (obj == null)
            throw new ArgumentNullException(nameof(obj));

        var keyValues = obj.GetPropertiesAsDictionary();

        var formUrlEncodedContent = new FormUrlEncodedContent(keyValues);

        return await formUrlEncodedContent.ReadAsStringAsync();
    }

    public static T Deserialize<T>(string formUrlEncodedText) where T : new()
    {
        if (string.IsNullOrEmpty(formUrlEncodedText))
            throw new ArgumentException("Form URL Encoded text was null or empty.", nameof(formUrlEncodedText));

        var pairs = formUrlEncodedText.Split('&');

        var obj = new T();

        foreach (var pair in pairs)
        {
            var nameValue = pair.Split('=');

            if (HasValue(nameValue))
            {
                obj.SetProperty(nameValue[0], nameValue[1]);
            }
        }

        return obj;
    }

    private static bool HasValue(string[] nameValue)
    {
        return nameValue.Length == 2 && nameValue[1] != string.Empty;
    }
}

public static class ObjectExtensions
{
    public static void SetProperty(this object source, string propertyName, object propertyValue)
    {
        var pi = source.GetProperty(propertyName);

        if (pi != null && pi.CanWrite)
        {
            pi.SetValue(source, propertyValue, null);
        }
    }

    public static PropertyInfo GetProperty(this object source, string propertyName)
    {
        BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.Instance;

        return source.GetType().GetProperty(propertyName, bindingFlags);
    }

    public static IDictionary<string, string> GetPropertiesAsDictionary(this object source)
    {
        var dict = new Dictionary<string, string>();

        if (source == null)
            return dict;

        var properties = source.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public);

        foreach (var property in properties)
        {
            var value = property.GetValue(source);

            if (value == null)
                continue;

            dict.Add(property.Name, value.ToString());
        }

        return dict;
    }
}

EDIT: Replaced ToKeyValues with GetPropertiesAsDictionary.

Answer 3

You could use Microsoft.AspNetCore.WebUtilities.FormReader to deserialize x-www-form-urlencoded content to a dictionary like so:

static Dictionary<string, StringValues> DeserializeForm(string content) {
    using var reader = new FormReader(content);
    return reader.ReadForm();
}

Answer 4

One liner linq for this is:

Dictionary<string,string> ParamsDict = ReceivedData.Split('&').Select(x => x.Split('=')).ToDictionary(key => key[0].Trim(), value => value[1].Trim());