How to set Content-Type header for HttpClient request in C#?

Hi everyone! I'm new to C# and trying to send a POST request using HttpClient. I need to set the content type as application/json, but I can't figure out how to do it correctly. I've tried different ways, but I'm getting 400 Bad Request errors from the server. Here's my current code: ```csharp using (var client = new HttpClient()) { var data = new { Name = "Test", Value = 123 }; var json = JsonSerializer.Serialize(data); // Trying to set Content-Type client.DefaultRequestHeaders.Add("Content-Type", "application/json"); var response = await client.PostAsync("https://api.example.com/data", new StringContent(json)); } ``` But when I run this code, I get an exception: "Misused header name. Ma