如何检查Request.QueryString是否为空

Question

I have my own HandleErrorAttribute , which reads data from Exception and HttpContext , insert them into template and send an e-mail to administrator. It usually works fine, but it some cases it breaks, when trying to check if QueryString is not empty.

var requestParams = "";
if (context.Request.QueryString != null && context.Request.QueryString.Keys.Count > 0)
{
    foreach (String key in context.Request.QueryString.Keys)
    {
        requestParams += key + ": " + context.Request.QueryString[key] + "<br />";
    }
}
else
{
    requestParams = "[ no query string data ]";
}

It breaks when checking condition ( NullReferenceException ), even if I can see in debug, that QueryString is not null and the Keys.Count is equal to 0.

What am I missing here? How to do a proper check for an empty QueryString ?

Stacktrace:

w System.Web.Hosting.IIS7WorkerRequest.GetQueryStringPtr(Int32& length)
w System.Web.Hosting.IIS7WorkerRequest.GetQueryStringRawBytes()
w System.Web.HttpRequest.get_QueryStringBytes()
w System.Web.HttpRequest.FillInQueryStringCollection()
w System.Web.HttpRequest.EnsureQueryString()
w System.Web.HttpRequest.get_QueryString()
w System.Web.HttpRequestWrapper.get_QueryString()
w project.Infrastructure.Attributes.ErrorHandlingAttribute.BuildErrorEmail(Exception exc, HttpContextBase context) w c:\Users\Marcin Bigoraj\Documents\Visual Studio 2012\Projects\project\Infrastructure\Attributes\ErrorHandlingAttribute.cs:wiersz 141
w project.Infrastructure.Attributes.ErrorHandlingAttribute.<>c__DisplayClass2.<OnException>b__1() w c:\Users\Marcin Bigoraj\Documents\Visual Studio 2012\Projects\project\Infrastructure\Attributes\ErrorHandlingAttribute.cs:wiersz 182
w System.Threading.Tasks.Task.InnerInvoke()
w System.Threading.Tasks.Task.Execute()

Answer 1

Check this code

if (Request.QueryString.Keys.Count > 0)
{

}

Answer 2

You can determine if there are any values in the QueryString by checking its count:

Request.QueryString.Count > 0;

It is sufficient.