How do you test your Request.QueryString[] variables?

Question

I frequently make use of Request.QueryString[] variables.

In my Page_load I often do things like:

       int id = -1;

             


        

Answer 1

if(!string.IsNullOrEmpty(Request.QueryString["id"]))
{
//querystring contains id
}

Answer 2

I actually have a utility class that uses Generics to "wrap" session, which does all of the "grunt work" for me, I also have something almost identical for working with QueryString values.

This helps remove the code dupe for the (often numerous) checks..

For example:

public class QueryString
{
    static NameValueCollection QS
    {
        get
        {
            if (HttpContext.Current == null)
                throw new ApplicationException("No HttpContext!");

            return HttpContext.Current.Request.QueryString;
        }
    }

    public static int Int(string key)
    {
        int i; 
        if (!int.TryParse(QS[key], out i))
            i = -1; // Obviously Change as you see fit.
        return i;
    }

    // ... Other types omitted.
}

// And to Use..
void Test()
{
    int i = QueryString.Int("test");
}

NOTE:

This obviously makes use of statics, which some people don't like because of the way it can impact test code.. You can easily refactor into something that works based on instances and any interfaces you require.. I just think the statics example is the lightest.

Hope this helps/gives food for thought.

Answer 3

I modified Bryan Watts' answer so that if the param your asking does not exist and you have specified a nullable type it will return null :

public static T GetValue<T>(this NameValueCollection collection, string key)
    {
        if (collection == null)
        {
            return default(T);
        }

        var value = collection[key];

        if (value == null)
        {
           return default(T);
        }

        var type = typeof(T);

        if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
        {
            type = Nullable.GetUnderlyingType(type);
        }

        var converter = TypeDescriptor.GetConverter(type);

        if (!converter.CanConvertTo(value.GetType()))
        {
            return default(T);
        }

        return (T)converter.ConvertTo(value, type);
    }

You can now do this :

Request.QueryString.GetValue<int?>(paramName) ?? 10;

Answer 4

I do have functions for each (actually it's one small class, with lots of statics):

• GetIntegerFromQuerystring(val)
• GetIntegerFromPost(val)
• ....

It returns -1 if fails (which is almost always OK for me, I have some other functions for negative numbers as well).

Dim X as Integer = GetIntegerFromQuerystring("id")
If x = -1 Then Exit Sub

Answer 5

Below is an extension method that will allow you to write code like this:

int id = request.QueryString.GetValue<int>("id");
DateTime date = request.QueryString.GetValue<DateTime>("date");

It makes use of TypeDescriptor to perform the conversion. Based on your needs, you could add an overload which takes a default value instead of throwing an exception:

public static T GetValue<T>(this NameValueCollection collection, string key)
{
    if(collection == null)
    {
        throw new ArgumentNullException("collection");
    }

    var value = collection[key];

    if(value == null)
    {
        throw new ArgumentOutOfRangeException("key");
    }

    var converter = TypeDescriptor.GetConverter(typeof(T));

    if(!converter.CanConvertFrom(typeof(string)))
    {
        throw new ArgumentException(String.Format("Cannot convert '{0}' to {1}", value, typeof(T)));
    }

    return (T) converter.ConvertFrom(value);
}