Configure Content

FluentHttpClient provides a comprehensive set of extensions for attaching request content to an HttpRequestBuilder. These methods cover raw HttpContent, string content, JSON, XML, form-encoded payloads, and optional buffering.

Adding HttpContent

Use this when you already have a concrete HttpContent instance.

var multipart = new MultipartFormDataContent();
// ... add files, fields, etc.

var builder = client
    .UsingBase()
    .WithContent(multipart);

• Assigns the provided HttpContent directly.
• Ideal for multipart uploads, streams, or custom content types.

String Content

These methods construct a StringContent payload with optional encoding and media type.

Basic String

builder.WithContent("raw text");

With Encoding

builder.WithContent("raw text", Encoding.UTF8);

With Media Type

builder.WithContent("raw text", "text/plain");

With Encoding and Media Type

builder.WithContent("raw text", Encoding.UTF8, "text/plain");

With MediaTypeHeaderValue

builder.WithContent("payload", new MediaTypeHeaderValue("application/custom"));

All overloads generate a StringContent instance and optionally set the Content-Type header.

JSON Content

JSON content can be supplied as raw JSON strings or objects that will be serialized using System.Text.Json.

AOT and JSON

For Native AOT builds, only the section for raw JSON strings applies. For typed JSON serialization, see the JSON AOT Support documentation for AOT-friendly overloads.

Raw JSON strings

builder.WithJsonContent("{ \"example\": true }");

Overloads support:

• Custom encoding
• Custom media type string or custom MediaTypeHeaderValue

Typed JSON serialization

builder.WithJsonContent(myObject);

You may also specify:

• Custom JsonSerializerOptions
• Custom media type string or custom MediaTypeHeaderValue

Example:

var options = new JsonSerializerOptions { WriteIndented = true };
builder.WithJsonContent(myObject, options, "application/ld+json");

All JSON extensions serialize the object, create StringContent, and apply the relevant media type.

XML Content

These methods attach XML content either from raw XML or using System.Xml.Serialization to serialize objects.

AOT and XML

For Native AOT buids, only the section for raw XML strings applies. FluentHttpClient does not have typed XML serialization overloads that are AOT-friendly.

Raw XML strings

builder.WithXmlContent(xmlString);

Overloads allow:

• Custom encoding
• Custom media type string or custom MediaTypeHeaderValue

Typed XML serialization

builder.WithXmlContent(myObject);

You can refine XML serialization with:

• Custom XmlWriterSettings
• Custom media type string or custom MediaTypeHeaderValue

Example:

var settings = new XmlWriterSettings { Indent = true, Encoding = Encoding.UTF8 };
builder.WithXmlContent(myObject, settings, "application/custom+xml");

These extensions serialize the object to XML and set it as the request content. If you specify an Encoding in the XmlWriterSettings, that encoding is used both during XML serialization and as the encoding applied to the resulting StringContent.

FormUrlEncodedContent Content

Produces standard application/x-www-form-urlencoded content.

From Dictionary

builder.WithFormContent(new Dictionary<string, string>
{
    ["username"] = "scott",
    ["password"] = "secret"
});

From Key/Value Pairs

Supports repeated keys.

var data = new[]
{
    new KeyValuePair<string, string>("role", "admin"),
    new KeyValuePair<string, string>("role", "editor")
};

builder.WithFormContent(data);

Buffering Request Content

Some HTTP handlers or intermediaries require the request body to be fully in memory so Content-Length is known ahead of time.

When buffering helps

• Servers that reject chunked uploads.
• Request signing systems requiring canonical byte sequences.
• Retry logic that must re-send identical content.
• Middleware that reads or rewinds the request body.

When buffering hurts

• Large payloads dramatically increase memory usage.
• Not suitable for true streaming scenarios.
• Should be used only when required.

Enable Buffering

builder.WithBufferedContent();

Sets BufferRequestContent = true so the content is fully written into memory before sending.

Behavior Notes

• Assigning content overrides any previously set content.
• JSON and XML extensions use UTF-8 by default.
• MediaTypeHeaderValue overloads bypass default media types.
• Streaming content may require buffering depending on the underlying handler.

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Quick Reference

Method	Purpose
WithContent(HttpContent)	Attach any existing HttpContent instance.
WithContent(string, ...)	String content with optional encoding/media type.
WithJsonContent(...)	Raw JSON or typed JSON serialization.
WithXmlContent(...)	Raw XML or typed XML serialization.
WithFormContent(...)	URL-encoded form data (dictionary or pairs).
WithBufferedContent()	Force buffering when required by handlers.