Convert a Dictionary to string of url parameters?

Question

Is there a way to convert a Dictionary in code into a url parameter string?

e.g.

// An example list of parameters
Dictionary<string, object> parameters ...;
foreach (Item in List)
{
    parameters.Add(Item.Name, Item.Value);
}

string url = "http://www.somesite.com?" + parameters.XX.ToString();

Inside MVC HtmlHelpers you can generate URLs with the UrlHelper (or Url in controllers) but in Web Forms code-behind the this HtmlHelper is not available.

string url = UrlHelper.GenerateUrl("Default", "Action", "Controller", 
    new RouteValueDictionary(parameters), htmlHelper.RouteCollection , 
    htmlHelper.ViewContext.RequestContext, true);

How could this be done in C# Web Forms code-behind (in an MVC/Web Forms app) without the MVC helper?

Solution 1

One approach would be:

var url = string.Format("http://www.yoursite.com?{0}",
    HttpUtility.UrlEncode(string.Join("&",
        parameters.Select(kvp =>
            string.Format("{0}={1}", kvp.Key, kvp.Value)))));

You could also use string interpolation as introduced in C#6:

var url = $"http://www.yoursite.com?{HttpUtility.UrlEncode(string.Join("&", parameters.Select(kvp => $"{kvp.Key}={kvp.Value}")))}";

And you could get rid of the UrlEncode if you don't need it, I just added it for completeness.

Solution 2

Make a static helper class perhaps:

public static string QueryString(IDictionary<string, object> dict)
{
    var list = new List<string>();
    foreach(var item in dict)
    {
        list.Add(item.Key + "=" + item.Value);
    }
    return string.Join("&", list);
}

Solution 3

You can use QueryHelpers from Microsoft.AspNetCore.WebUtilities:

string url = QueryHelpers.AddQueryString("https://me.com/xxx.js", dictionary);

Solution 4

the most short way:

string s = string.Join("&", dd.Select((x) => x.Key + "=" + x.Value.ToString()));

But shorter does not mean more efficiency. Better use StringBuilder and Append method:

first = true;
foreach(var item in dd)
{
    if (first)
        first = false;
    else
        sb.Append('&');
    sb.Append(item.Key);
    sb.Append('=');
    sb.Append(item.Value.ToString());
}

Solution 5

I'm not saying this option is better (I personally think it's not), but I'm here just to say it exists.

The QueryBuilder class:

var queryStringDictionary = new Dictionary<string, string>
{
    { "username", "foo" },
    { "password", "bar" }
};

var queryBuilder = new QueryBuilder(queryStringDictionary);
queryBuilder.Add("type", "user");

//?username=foo&password=bar&type=user
QueryString result = queryBuilder.ToQueryString();

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