WebException how to get whole response with a body?

var resp = new StreamReader(ex.Response.GetResponseStream()).ReadToEnd();

dynamic obj = JsonConvert.DeserializeObject(resp);
var messageFromServer = obj.error.message;

try {
 WebClient client = new WebClient();
 client.Encoding = Encoding.UTF8;
 string content = client.DownloadString("https://sandiegodata.atlassian.net/wiki/pages/doaddcomment.action?pageId=524365");
 Console.WriteLine(content);
 Console.ReadKey();
} catch (WebException ex) {
 var resp = new StreamReader(ex.Response.GetResponseStream()).ReadToEnd();
 Console.WriteLine(resp);
 Console.ReadKey();
}

This only improves on the existing answers. I have written a method that takes care of the details of throwing/rethrowing with an enhanced message, that includes the response body:

Here's my code (in Client.cs):

/// <summary>
///     Tries to rethrow the WebException with the data from the body included, if possible. 
///     Otherwise just rethrows the original message.
/// </summary>
/// <param name="wex">The web exception.</param>
/// <exception cref="WebException"></exception>
/// <remarks>
///     By default, on protocol errors, the body is not included in web exceptions. 
///     This solutions includes potentially relevant information for resolving the
///     issue.
/// </remarks>
private void ThrowWithBody(WebException wex) {
    if (wex.Status == WebExceptionStatus.ProtocolError) {
        string responseBody;
        try {
            //Get the message body for rethrow with body included
            responseBody = new StreamReader(wex.Response.GetResponseStream()).ReadToEnd();

        } catch (Exception) {
            //In case of failure to get the body just rethrow the original web exception.
            throw wex;
        }

        //include the body in the message
        throw new WebException(wex.Message + $" Response body: '{responseBody}'", wex, wex.Status, wex.Response);
    }

    //In case of non-protocol errors no body is available anyway, so just rethrow the original web exception.
    throw wex;
}

You use it in a catch clause much like the OP showed:

//Execute Request, catch the exception to eventually get the body
try {
    //GetResponse....
    }
} catch (WebException wex) {
    if (wex.Status == WebExceptionStatus.ProtocolError) {
        ThrowWithBody(wex);
    }

    //otherwise rethrow anyway
    throw;
}