Adding resources to an assembly

The C# Column - Yashawant Kanetkar

An assembly can contain resource files. An assembly containing resources is known as a satellite assembly. A resource file can contain any resource such as text, string tables, pictures, etc. The resource file can be embedded inside the assembly. In this article we plan to create a resource file called ‘quotes.resources’ in an application called res and embed this file in another assembly called resclient. The ‘quotes.resources’ file would contain five images and five quotes as resources. The assembly in which we would embed this file will simply pick out a random image and a quote and display them on a form. Let us first see how to build a resource file.

Create a Console Application. Add the following code in the Main( ) method.

using System;
using System.Resources;
using System.Drawing;
static void Main ( string[ ] args )
{
   ResourceWriter rw = new ResourceWriter(“quotes.resources”);
   Image img0 = Image.FromFile(“heart.jpg”);
   Image img1 = Image.FromFile(“fire.jpg”);
   Image img2 = Image.FromFile(“face02.jpg”);
   Image img3 = Image.FromFile(“face03.jpg”);
   Image img4 = Image.FromFile(“face05.jpg”);
   rw.AddResource(“img0”, img0);
   rw.AddResource(“img1”, img1);
   rw.AddResource(“img2”, img2);
   rw.AddResource(“img3”, img3);
   rw.AddResource(“img4”, img4);
   rw.AddResource(“quo0”, “Health is wealth”);
   rw.AddResource(“quo1”, “A long journey starts with a single 
step”);
   rw.AddResource(“quo2”, “Better late than never but better  
never late”);
   rw.AddResource(“quo3”, “Opportunity knocks for those who 
listen”);
   rw.AddResource(“quo4”, “The best time to make a friend is 
before you need one”);
   rw.Close();
}

After creating a ResourceWriter reference we have we created five Image references img0 through img4 and initialised them with images from five different files. Next we added these resources in the file using the AddResource( ) method of the ResourceWriter class. The first argument of the method specifies the key and the second argument specifies the image object to be added. The key that we have added is in the form imgnumber. Note that the image files must either be in the ‘bin/debug’ folder or their path must be specified.

Next we have added five quotes to the same file with the key format quonumber. Then we have closed the ResourceWriter by calling the Close( ) method.

On executing this application a file called ‘quotes.resources’ gets created. Now let us see how to embed this file in another assembly. For this we have created a simple windows forms application called resclient and added a PictureBox named pic and a Label named quote to it. We have changed the font size and colour of the text that would get displayed in the label using the ‘Properties’ window.

To embed the resource file we need to select the ‘Add | Add Existing Item’ from the context menu that pops up on right-clicking the Solution Explorer. Select the ‘quotes.resource’ file. The file gets displayed in the Solution Explorer. In the Properties window of this resource file change the BuildAction from None to Embedded Resource so that the resource gets embedded into the output assembly. The ‘Properties’ window is shown in the following figure.

After this much is done, we have added code to the constructor of the form class to display a quote and a picture in the form. The constructor is given below:

public Form1()
{
   InitializeComponent();
   Assembly asm = Assembly.GetExecutingAssembly();
   ResourceManager rm = new ResourceManager(“resclient.quotes”,
asm);
   Random r = new Random();
   string str;
   int i = r.Next(4);
   str = string.Format( “img{0}”, i);
   pic.Image = (Image)rm.GetObject(str);
   i = r.Next(4);
   str = string.Format(“quo{0}”, i);
   tip.Text = (string) rm.GetObject(str);
   }

To use the embedded resource, we have used the ResourceManager class defined in the System.Resources namespace. We need to pass the reference of the Assembly class where the resources are embedded to the constructor of the ResourceManager class. In this case the file is embedded in the executing assembly, so we have passed the result of Assembly.GetExecutingAssembly( ) as the second argument. The first argument is the root name of the resource file. The root name is made of the namespace followed by the name of the resource file without extension. We have collected the reference of this ResourceManager object in rm.

To extract a resource from the file we have used the GetObject( ) method. We have passed a key to this method. This method returns us the object associated with the key specified. To create the key we have used the Random class’s Next( ) method that would return any number between 0 and 4 (0 & 4 inclusive). Next we have set the Image property of pic and Text property of quote to the Image and string objects respectively returned by the GetObject( ) method. The output of this application is shown in the following figure.

Every time we execute this application we get a different picture and quote on the form.

Yashavant Kanetkar, one of the first Express Computer columnists, is an established software expert, speaker and author with several best-sellers to his credit, including titles like “Let Us C” and the “Fundas” series. Contact him at kanet@nagpur.dot.net.in