Reason behind GET/DELETE cannot have body in webapi

Question

Why do HttpMethods such as GET and DELETE cannot contain body?

public Task<HttpResponseMessage> GetAsync(Uri requestUri);
public Task<HttpResponseMessage> DeleteAsync(string requestUri);

also in Fiddler, if I supply a body, the background turns red. But still it will execute with body on it.

So as an alternative, I used SendAsync() because it accepts HttpRequestMessage which can contain HttpMethod as well as the content.

// other codes
Category category = new Category(){ Description = "something" };
string categoryContent = JsonConvert.SerializeObject(category);
string type = "application/json";

HttpRequestMessage message = new HttpRequestMessage(HttpMethod.Delete, "-page-")
HttpContent content = new StringContent(categoryContent, Encoding.UTF8, type);
HttpClient client = new HttpClient();

message.Content = content;
await client.SendAsync(message, HttpCompletionOption.ResponseHeadersRead);
// other codes

Did I missed something else?

Answer 1

Per HTTP standards, GET method is aimed to retrieve data, hence there is no need to provide a request body.

Adding a request body violates the rules defined. This is therefore prohibited.

The same applies to DELETE method.