How to build query string for System.Net.HttpClient GET Request

In this post I will explain multiple ways to use parameters for HTTP GET Request using System.Net.HttpClient. You don't need to build parameters string by concatenating different values from a name-value collection.

• First method is to use HttpUtility.ParseQueryString() function.

  var query = HttpUtility.ParseQueryString(string.Empty);
  query["p1"] = "value1";
  query["p2"] = "value2";
  string queryString = query.ToString();
    

  queryString variable contains the parameters in query string format.

• Another way could be to use UriBuilder class.

  var builder = new UriBuilder("http://example.com");
  builder.Port = -1;
  
  var query = HttpUtility.ParseQueryString(builder.Query);
  query["p1"] = "value1";
  query["p2"] = "value2";
  builder.Query = query.ToString();
  
  string url = builder.ToString();
    

  The url variable will contain both the page URL and query string parameters.

• If you do not want to include a reference to System.Web in your project, you can use FormDataCollection class by adding reference to System.Net.Http.Formatting.

  var parameters = new Dictionary()
  {
   { "p1", "value1" },
   { "p2", "value2 + SomeOtherValue?" },
  }; 
  
  var queryString = new FormDataCollection(parameters).ReadAsNameValueCollection().ToString();
    

  queryString variable now contains the parameters in query string format.

• If you are using ASP.Net Core, you can use the QueryHelpers class by first adding reference to Microsoft.AspNetCore.WebUtilities.

  var query = new Dictionary
  {
   ["p1"] = "value1",
   ["p2"] = "value2",
  };
  
  var response = await client.GetAsync(QueryHelpers.AddQueryString("/api/", query));