Simplest WPF/C# debugging method to check what is going on

With C++/C, the easiest way of debugging is to use cout/printf to print out what is going on to the console.

What would be the equivalent method in WPF/C#?

I thought about using MessageBox(), but WPF doesn't seem to support this function. I also thought about using logging function, but I wonder it's too complicated than printf/cout.

I can use break points in Visual Studio, even so, I need some command to set a break point.

if (ABC())
{
    // What command should be here to set a break point?
}