I was trying to send a discord webhook with C# like this:

public class DiscordWebhook(string content)
{
    public string content { get; set; } = content;
}

...


var message = "```ansin";

foreach (var pl in top10)
{
    var sb = new StringBuilder(Plugin.Config.WebhookMessage);

    ...

    message += sb + "n";
}

message += "```";

PostSendMessage(JsonSerializer.ToJsonString(new DiscordWebhook(message)));

...

public async Task PostSendMessage(string messageContent)
{
    using var client = new HttpClient();
    var content = new StringContent(messageContent, Encoding.UTF8, "application/json");

    try
    {
        var response =
            await client.PostAsync(
                $"https://discord.com/api/webhooks/{Plugin.Config.WebhookId}/{Plugin.Config.WebhookToken}",
        content);
        Log.Info(response.Content.ReadAsStringAsync().Result);
        response.EnsureSuccessStatusCode();
    }
    catch (HttpRequestException e)
    {
        Log.Error(e);
    }
}

but the 400 Bad Request Error Happens:
{"message": "The request body contains invalid JSON.", "code": 50109}

Logged the JsonSerializer.ToJsonString(new DiscordWebhook(message)), paste into nodejs and sent a request, and it was working. It works when I remove the code block (“`)