In this project we will be building a digital clock in C# using Visual Studio. Now we need to add the event handler method t_Tick to our timer t. May 07, 2018 Visual Studio for Mac version 7.5 now supports.NET Core 2.1 RC. Major improvements include faster build performance, better compatibility with.NET Framework, and closing gaps in both ASP.NET Core and EF Core. You can read more about the.NET Core 2.1 RC release in the announcement blog post.
Note You may recognize object sender at the top of the event handler as the same one used in the tutorial. Because you hooked up different label control click events to a single event handler method, the same method is called no matter which label the user chooses. The event handler method needs to know which label was chosen, so it uses the name sender to identify the label control. The first line of the method tells the program that it's not just a generic object, but specifically a label control, and that it uses the name clickedLabel to access the label's properties and methods. This method first checks whether clickedLabel was successfully converted (cast) from an object to a label control. If unsuccessful, it has a value of null (C#) or Nothing (Visual Basic), and you don't want to execute the remainder of the code in the method. Next, the method checks the chosen label's text color by using the label's ForeColor property.
If the label's text color is black, then that means the icon's already been chosen and the method is done. (That's what the return statement does: It tells the program to stop executing the method.) Otherwise, the icon hasn't been chosen, so the program changes the label's text color to black. On the menu bar, choose File Save All to save your progress, and then, on the menu bar, choose Debug Start Debugging to run your program. You should see an empty form with a blue background.
Choose any of the cells in the form, and one of the icons should become visible. Continue choosing different places in the form. As you choose the icons, they should appear.
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