How to copy data to clipboard in C#

How can I copy a string (e.g "hello") to the System Clipboard in C#, so next time I press CTRL+V I'll get "hello"?

There are two classes that lives in different assemblies and different namespaces.

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WinForms: use following namespace declaration, make sure Main is marked with [STAThread] attribute:

using System.Windows.Forms;

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WPF: use following namespace declaration

using System.Windows;

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console: add reference to System.Windows.Forms, use following namespace declaration, make sure Main is marked with [STAThread] attribute. Step-by-step guide in another answer

using System.Windows.Forms;

To copy an exact string (literal in this case):

Clipboard.SetText("Hello, clipboard");

To copy the contents of a textbox either use TextBox.Copy() or get text first and then set clipboard value:

Clipboard.SetText(txtClipboard.Text);

See here for an example.
Or... Official MSDN documentation or Here for WPF.

Remarks:

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Clipboard is desktop UI concept, trying to set it in server side code like ASP.Net will only set value on the server and has no impact on what user can see in they browser. While linked answer lets one to run Clipboard access code server side with SetApartmentState it is unlikely what you want to achieve.

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If after following information in this question code still gets an exception see "Current thread must be set to single thread apartment (STA)" error in copy string to clipboard

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This question/answer covers regular .NET, for .NET Core see - .Net Core - copy to clipboard?

Stack Overflow Q#3546016, score: 983