CaptureHttpTrafficTests.cs

private async Task OnRequestModifyTrafficEventHandler(object sender, SessionEventArgs e)
{
    var method = e.WebSession.Request.Method.ToUpper();

    if ((method == "POST" || method == "PUT" || method == "PATCH" || method == "GET"))
    {
        //Get/Set request body bytes
        byte[] bodyBytes = await e.GetRequestBody();
        await e.SetRequestBody(bodyBytes);

        //Get/Set request body as string
        string bodyString = await e.GetRequestBodyAsString();
        await e.SetRequestBodyString(bodyString);
    }
}