Powershell 中 catch webexception

try{
        $resp = $r.GetResponse()
        $reqstream = $resp.GetResponseStream()
        $sr = new-object System.IO.StreamReader $reqstream
        $sr.ReadToEnd()
    }
    catch [Net.WebException]
    {
        if($_.Exception.Response -eq $null)
        {
            return 100
        }
         
        $sr = New-Object System.IO.StreamReader($_.Exception.Response.GetResponseStream()) 
        $errorcode = [int] ($_.Exception.Response.StatusCode)
        Throw "Error Code : $errorcode, "  + $sr.ReadToEnd()     
    }

var resp = new HttpResponseMessage(HttpStatusCode.BadRequest)
                        {
                            Content = new StringContent("xxxx!"),
                            ReasonPhrase = "xxxx!"
                        };

                        throw new HttpResponseException(resp);