When does the .NET framework need to be installed on a client machine?

Question

I'm not entirely sure when the .NET framework needs to be installed on a client's machine when building C# apps.

Say for instance there is a console application as such:

using System;
using System.IO;
using System.Windows.Forms;

namespace HelloWorld{
    class Hello {
        static void Main() {                    
             MessageBox.Show("Hello World.");
        }
    }
}

Would the client be required to install the .NET run times? Could this be bypassed by including the System.Windows.Forms.dll and merging it in the exe?

Thanks

Answer 1

.NET Framework must be installed. Even if you embed parts of the .NET framework into your assembly (eg. using Fody/Costura) or include them as DLLs, .NET framework assemblies are almost never standalone. For example, System.Windows.Forms.dll would reference parts of the .NET framework that are external to System.Windows.Forms.dll.

Luckily, .NET framework is usually installed on Windows by default, so to make life easy you could just target a certain version of Windows. For example, I usually target 4.0 and assume the user is running Windows 7 SP1 or later. Anyone with up-to-date Windows 7 should be running SP1 as it's a Windows Update.

Here is a table of which .NET versions come on which OS (source).

Windows Version | Default .NET
==============================
XP              | None
Vista           | 3.0
7               | 3.5
7 SP1           | 4.0
8               | 4.5
8.1             | 4.5.1
10              | 4.6

If you need to know how to change the target framework, try this link. Basically, go to the project properties and change "Target Framework".