Of solutions, projects and items

The C# Column - Yashawant Kanetkar

The .NET architecture has provided a systematic organisation of files, folders, data connections and references used in a program. The organisation comes in the form of solutions and projects. A solution is a container for one or more related projects, whereas, a project is a container of various items comprising the application.

Multi-projects solution

As said above, a solution can contain one or more projects. In addition to projects, a solution can also contain solution items and miscellaneous items. We will take a look at these items later in this article. A solution automatically gets created when we create a project and carries the same name as the project. However, we can choose to create separate folders for solutions and projects by selecting the ‘Create directory for Solution’ checkbox that appears on the ‘New Project’ dialog box.

But when are we required to create multiple projects in one solution? There are many scenarios when such a need arises. Suppose we have created an assembly exporting a method that converts rupees to dollars and returns dollars as an integer value. Then we create a console application as a client of this assembly. We could close the project containing the assembly and create the client application in the same instance of the IDE.

After the client is run successfully, at one point we decide that the exported method should return a float value so as to return the exact converted value. So, we again close the client project and re-open the assembly project, make changes in it and re-open the client project to test the assembly. Someone would keep two instances of the Visual Studio.NET IDE open and work in them simultaneously. Now, what if we want to create two clients—one of them as a console application and another as a form-based application. In such a case instead of keeping many instances open, we can create all these projects in the same solution.

Creating multiple projects in one solution enables us to manage and work on the projects in one instance of the IDE. If we set the options or change the settings, they apply to the group of projects. Again, we can use the Solution Explorer window to manage and view all the projects and their items at a glance.

The information about the projects is stored in two files ‘.sln’ (solution definition file) and ‘.suo’ (solution user options file). The solution definition file stores the meta-data that defines the solution, projects that are associated with the solution and items that you want to be available to all the projects. It also contains any ‘Build’ configurations created at the solution level. The ‘.suo’ file stores information about the options that customise the IDE.

Let us see how to create and manage multiple projects in a solution. Create a Class Library project named ‘rupeetodollar’. Define a method in it as shown below:

public float todollar(int r)
{ 
  	return (r * 47.50f);
}

Create a console application as the client of the ‘rupeetodollar.dll’ assembly. While creating the project, select the ‘Add to Solution’ radio button on the ‘New Project’ dialog box. After the project is created, Solution Explorer displays the visual representation of solution as shown in the adjoining figure.

The project ‘rupeetodollar’ appears in bold type. This is because it is, by default, set as the start-up project. The start-up project is the one that gets executed when Ctrl+F5 is pressed. We can change the Start-up project by right-clicking the project name in Solution Explorer and selecting the ‘Set as StartUp Project’ menu item. Although only the startup project is executed, every time we build the solution (or press Ctrl+F5), all its projects get built.

We can even select which project to build and which not to build. For this, go to the Properties window of the solution. Select ‘Configuration Properties’ item. The right hand side pane displays the build configuration options. Uncheck the ‘Build’ check box for the project you don’t want to build and click the OK button. Now if you build the solution only those projects that are selected will get built. In the ‘rupeetodollar’ example, once the assembly is created, we don’t want to build it again (unless we change it). So, we can very well choose not to build it.

We are going to create two clients for the ‘rupeetodollar’ assembly. In this case, to save the time, we can run both the client projects simultaneously by setting the multiple startup projects. For this, go to the Properties window of the solution. Select the ‘Multiple Startup Projects’ radio button as shown in the following figure:

Only selecting multiple startup projects option is not sufficient. We must also select some action for the project. We have selected ‘Start without debugging’ from the ‘Action’ list for the client projects. Click the OK
button.

Add the references of the ‘rupeetodollar.dll’ assembly in both the projects and add the following code snippet in the console application.

rupeetodollar.convert c = new rupeetodollar.convert();
float d = c.todollar (10);
Console.WriteLine (d);

Add the following code snippet in the form-based application.

rupeetodollar.convert c = new rupeetodollar.convert();
float d = c.todollar(10);
MessageBox.Show (d.ToString());

Press Ctrl+F5. You will see the output of both the projects simultaneously.

Adding too many projects to a solution may make working with the solution slow. For example, opening the solution in IDE takes more time. We can improve the working time by temporarily excluding the project that we don’t require often from the solution. To do so, select the project and select the ‘Projects | Unload Project’ menu item. The unloaded project doesn’t get built. We can reload it by right clicking it and selecting ‘Reload Project’ from the pop-up menu.

Solution items

Sometimes we need items that are useful in developing the application but do not belong to any particular project. These items are called as ‘Solution Items’ and are displayed under ‘Solution Items’ node in the Solution Explorer. These files don’t get built.

A style sheet is a common solution item. A style sheet can be used to format numerous Web pages in multiple projects. When the solution is re-opened, the style sheet file appears under the ‘Solution Items’ node in ‘Solution Explorer’. Actually, the file representing a solution item can be stored at any location on disk. The item displayed in the ‘Solution Items’ acts as a link to this file. The ‘.sln’ file tracks the path of the solution item file.

Miscellaneous files

Miscellaneous files are the ones that we use for development of an application but are not part of a project or solution. A common example of miscellaneous items are the ‘Readme.txt’ files that are shipped with the software. Similarly, development instructions, database schema, and code snippets are examples of miscellaneous items.

To create a miscellaneous item, select the ‘File | New | File’ option. Select a category and then select the template. Click ‘Open’ button. Add the contents to the file and save it. To display miscellaneous items in Solution Explorer we need to select the ‘Tools’ menu and then select ‘Options | Environment folder | Documents’. In the ‘Documents’ tab check the ‘Show miscellaneous files in Solution Explorer’ checkbox.

Project as container

A project acts as a container for source files, references, folders, etc, that are part of the application. The build information, configuration settings and details of project items are stored in the ‘.csproj’ file. If the project is part of a multi-project solution, we can open the individual project by opening the ‘.csproj’ file.

In every project two folders namely ‘bin’ and ‘obj’ are created. The ‘bin’ folder contains a sub-folder ‘Debug’. ‘Debug’ is the output directory of the application. An output directory stores the output file of a project that is typically ‘.exe’ or ‘.dll’. The ‘bin’ folder contains sub-folders ‘Debug’ or ‘Release’ depending upon the build configuration of the project. The following figure shows how a solution is organised.

The figure clearly indicates that Projects and Solution Items are part of a solution, Miscellaneous Items are not.

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