C#|.NET Query String in Uri

C#|.NET Query String in Uri

In a not-so-basic-application you might have pages which are used for multiple similar purposes. You pass query string with many fields with multiple values between such pages (or web pages). In database driven apps, parameter values could be user generated and stored in the back-end and you pull more info from database on the basis of the value in query parameter. This is not the scenario of back-end driven app. This is more about “Field Names” and Values, which are part of the design and known to you while coding, and you want to manage them effectively and make the code more readable.

Let’s take an example:

You have a page in your app which loads different lists (ex: city, state, pin, salutation, etc.) and lets user select an item from the list. At different places in your app you pop this page up with required parameters to load appropriate items. The call to page looks something like this:

this.NavigationService.Navigate("/ListPicker.xaml?ListType=city",UriKind.Relative)

Let’s assume your page also has the ability for editing and you want to activate appropriate functionality (select only || edit). You would add one more parameter to your query, like so:

this.NavigationService.Navigate("/ListPicker.xaml?ListType=city&FormType=select",UriKind.Relative)

If you have many such pages, each have multiple fields and their multiple values, and you make calls to these pages from different places in your code, soon it will be very difficult to manage hard-coded query strings in Uri’s.

Here comes enum based solution:

We will have enums for fields and their values. For the purpose of this example we will keep single enum for fields and multiple enums for values for different fields. Let’s code
First define enums for fields and their values:

        internal enum QueryFields { ListPicker_FormType, ListPicker_ListType };
        internal enum ListTypes { City, States, Zip, Salutation };
        internal enum FormTypes { Select, Edit };

If you do not wish to be more detailed, you could simply build your Uri’s like so:

This.NavigationService.Navigate("/ListPicker.xaml?{0}={1}",QueryFields.ListPicker_FormType.ToString(), FormTypes.Select.ToString());
//The resultant uri - /ListPicer.xaml?ListPicker_FormType=Select

We will see below how you could parse query parameters in the called page and retrieve values in enum types.

Creating Uri as above still has string formatting which is not easy to maintain in multiple uses. To make things manageable and less error prone, let’s create a new enum for pages in the app and shift Uri building code in a single method which could be called from anywhere in the app with different field and values.

        internal enum AppPages {ListPicker, Setting, Main, etc };
        internal static Uri GetUri(AppPages appPage, params KeyValuePair<string, string>[] args)
        {
            string uriString = "";
            switch (appPage)
            {
                case AppPages.ListPicker:
                    uriString = "/Views/ListPicker.xaml";
                    break;
                case AppPages.Setting:
                    uriString = "/Views/Settings.xaml";
                    break;
                case AppPages.Main:
                    uriString = "/Main.xaml";
                    break;
                default:
                    uriString = "/Main.xaml";
                    break;
            }
            int counter = 0;
            string seperator = "?";
            foreach(KeyValuePair<string, string> query in args)
            {
                if (counter > 0) seperator = "&";
                uriString = String.Format("{0}{1}{2}={3}", uriString, seperator, query.Key, query.Value);
            }
            return new Uri(uriString, UriKind.Relative);
        }

With GetUri, you could create page navigation Uri with enums only instead of hard-coded strings:

            KeyValuePair<string, string> query_1 = new KeyValuePair<string,string>(QueryFields.ListPicker_FormType.ToString(), FormTypes.Select.ToString());
            KeyValuePair<string, string> query_2 = new KeyValuePair<string,string>(QueryFields.ListPicker_ListType.ToString(), ListTypes.City.ToString());
            This.NavigationService.Navigate(GetUri(AppPages.ListPicker, query_1, query_2));

Once you are navigated to your page, you need to parse query strings and extract enums which you could use in the page to decide page’s functionality.

At page level you need to have required enum type fields. For this example we will have two fields, one FormTypes type and other ListTypes type. A private processQuery method which accepts a dictionary sets these two fields appropriately.

        FormTypes formType;
        ListTypes listType;
        private void processQuery(Dictionary<string, string> query)
        {
            string _formTypeName = "";
            string _listTypeName = "";
            query.TryGetValue(QueryFields.ListPicker_FormType.ToString(), out _formTypeName);
            query.TryGetValue(QueryFields.ListPicker_ListType.ToString(), out _listTypeName);
            if (_formTypeName.Length != 0) formType = (FormTypes)(Convert.ToInt32(_formTypeName));
            if (_listTypeName.Length != 0) listType = (ListTypes)(Convert.ToInt32(_listTypeName));
        }

You would call processQuery method from OnNavigatedTo method of your page.

        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            Dictionary<string, string> _params = new Dictionary<string, string>(NavigationContext.QueryString);
            processQuery(new Dictionary<string, string>());
        }

If you have 100’s of case statements (to choose a page) in GetUri, and you are concerned about performance, refactore the method to accept page name with path as string. With page path name directly in string, you would not need case statements. By the way, in my case with about 80+ cases to get PageName, the query creation does not take more than 50MS, which is negligible for me. More so, navigation calls are not recursive ones.

Transparent Live Tile For Windows Phone 8.1

Transparent Live Tile For Windows Phone 8.1

Windows Phone 8.1 Dev Preview

Windows Phone 8.1 developer preview is totally awesome. So what is one of the most important things app devs can do right away, without much fuss, to make their apps look great with Windows Phone 8.1? Revisit your app’s Live Tile images. Why? In 8.1, Start screen is mesmerizing with the parallax effect and Live Tile with background overlay. Dev preview users are going crazy with new Start experience, and I am sure, with public release, end users are going to love to have background image as well. Take a look at this awesome Nokia Lumia 925 Start screen:

wp_ss_20140416_0015[1]

When users have a background image, they might not like to have solid Live Tiles block their beautiful background. So, revisit your app’s Live Tile images – all of them! Check if they are transparent or not? If they are like Cortana, Avirall Time Suite, etc. in the image above, you are all set. You can safely ignore this article and find some other awesome way to improve your app for WP8.1 (think Cortana). If they are not, I suggest to update ‘em ASAP. And it’s easy, too. Let’s see how you can create transparent Live Tile images with Open Source Inkscape. You could choose to use Paint.NET (not MS Paint), Photoshop, GIMP, or any other tool which allows you to export image with transparency. Though I prefer GIMP for image editing but I chose Inkscape for this demo. Let’s go.

Step 1: Setup the page

InkScape01

  1. Open Inkscape and create a new document and Open Document Properties from file menu.
  2. In most cases app icons are solid white, if yours is one too, change the background color of the page, temporarily, to light yellow. This is while working only so that you can see white color. Before exporting we will reset this to transparent (this is very important).
  3. This example is for 336 X 336 medium tile. So set the custom size to 336 X 336.
  4. Make sure Units is “px”.

Step 2: Setup the drawing

InkScape02

Windows Phone 8 Asset Template Guide suggests a 336 X 336 tile to have 110px margin on all sides. Create 110px margin guides on all the sides. To create margin guides click and drag from the horizontal ruler on the top and from the vertical ruler on the left.

Step 3: Create Live Tile image of your app

InkScape03

The center part between the margins is the space where your tile image will go. Create your image here. For this example I simply dragged the box from tool box and made a hole in it 😀

Step 4: Set background to transparent

InkScape03a

To create a transparent Live Tile image we would like to have a transparent background. Go back in document properties and set Background to transparent by resetting “A” to 0. If your image is solid white, you might not see anything after making the background transparent. Don’t worry, your image is there (maybe somebody can tell how working space (not document background) in Inkscape can be made a different color than white).

Step 5: Export

InkScape04

  1. Open Export dialog from File > Export Bitmap…
  2. Set X0, X1, Y0, Y1 as shown in the image above.
  3. Browse for the image location, and make sure you give “PNG” as the extension of the image, NOT JPG or BMP.
  4. Export. (Alternatively, as suggested by Austin Andrews, you could export as SVG, and use his awesome service!)

Step 6: Check Final Image

WindowsPhotoViewer05

Notice that your final image does not have a white background. Windows Photo Viewers’s light blue background is your image’s background.

You are done. You would want to change all Live Tile images of your app in the same way. A transparent Live Tile image will encourage users to have your app pinned to Start screen without obstructing their beautiful background images.

Respect your users!