MultipartFormDataContent Add Extension Method to Accept Custom Header Values

By default MultipartFormDataContent.Add method has three overloads.

• Add(HttpContent content)
• Add(HttpContent content, string name)
• Add(HttpContent content, string name, string fileName)

In this post let’s see how we can add an extension method to MultipartFormDataContent to add a new overload method which will let us send additional parameters.

• Add(HttpContent content, string name, string fileName, object headerValues)

This is our Extension Method.

public static void Add(this MultipartFormDataContent form, HttpContent content, string name, string fileName, object headerValues)

{

    var header = new ContentDispositionHeaderValue("form-data")

    {

        Name = name,

        FileName = fileName

    };

    var headerParameters = new HttpRouteValueDictionary(headerValues);

    foreach (var parameter in headerParameters)

    {

        header.Parameters.Add(new NameValueHeaderValue(parameter.Key, parameter.Value.ToString()));

    }

    content.Headers.ContentDisposition = header;

    form.Add(content);

}

And this is how you can pass values.

using (var multipartFormDataContent = new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture)))

{

    multipartFormDataContent.Add(new StreamContent(new MemoryStream(data)), name, fileName, new

    {

        Parameter1="HelloWorld"

    });

}

This is how you can read the values.

MultipartMemoryStreamProvider provider = new MultipartMemoryStreamProvider();

await Request.Content.ReadAsMultipartAsync(provider);

Func<ICollection<NameValueHeaderValue>, string, string> GetHeaderValueByKey = (headerValues, key) =>

{

   if (headerValues == null)

       return null;

   NameValueHeaderValue nameValueHeaderValue = headerValues.FirstOrDefault(x => x.Name.Equals(key, StringComparison.OrdinalIgnoreCase));

   return nameValueHeaderValue != null ? nameValueHeaderValue.Value : null;

}; 

HttpContent file = provider.Contents.FirstOrDefault();

string parameter1Value = GetHeaderValueByKey(file.Headers.ContentDisposition.Parameters, "Parameter1");

Result

Happy Coding.

Regards,
Jaliya