Net4x.InputSimulator 2.2.0.26250

Net4x.InputSimulator

A small, dependency-free wrapper around the Win32 SendInput API for synthesising keyboard input, plus the key-state queries that go with it.

Originally written by Michael Noonan; this package repackages it for modern .NET while keeping the classic .NET Framework target alive.

Target frameworks

net45 · net6.0-windows · net8.0-windows · net10.0-windows

Windows only: the library P/Invokes into user32.dll.

Install

dotnet add package Net4x.InputSimulator

Usage

Everything lives on the static WindowsInput.InputSimulator class.

using WindowsInput;

// Type some text into whatever has focus.
InputSimulator.SimulateTextEntry("Hello, world!");

// Press a single key.
InputSimulator.SimulateKeyPress(VirtualKeyCode.RETURN);

// Hold a key down and release it later.
InputSimulator.SimulateKeyDown(VirtualKeyCode.SHIFT);
InputSimulator.SimulateKeyPress(VirtualKeyCode.VK_A);
InputSimulator.SimulateKeyUp(VirtualKeyCode.SHIFT);

// CTRL+C
InputSimulator.SimulateModifiedKeyStroke(VirtualKeyCode.CONTROL, VirtualKeyCode.VK_C);

// CTRL+SHIFT+ESC
InputSimulator.SimulateModifiedKeyStroke(
    new[] { VirtualKeyCode.CONTROL, VirtualKeyCode.SHIFT },
    VirtualKeyCode.ESCAPE);

// CTRL+K, CTRL+C style chords
InputSimulator.SimulateModifiedKeyStroke(
    VirtualKeyCode.CONTROL,
    new[] { VirtualKeyCode.VK_K, VirtualKeyCode.VK_C });

// Query the keyboard.
bool shiftHeld = InputSimulator.IsKeyDown(VirtualKeyCode.SHIFT);
bool shiftHeldNow = InputSimulator.IsKeyDownAsync(VirtualKeyCode.SHIFT);
bool capsLockOn = InputSimulator.IsTogglingKeyInEffect(VirtualKeyCode.CAPITAL);

API

The enums VirtualKeyCode, KeyboardFlag, MouseFlag, XButton and InputType mirror the constants in Winuser.h.

How SimulateTextEntry types things

• Printable characters (U+0020 and above, including non-BMP characters via their surrogate pair) are injected as Unicode packets, so they arrive verbatim no matter which keyboard layout is active.
• Line breaks — "\n", "\r" or the pair "\r\n" — press RETURN exactly once.
• Other control characters below U+0020 are resolved through VkKeyScan and injected as the real keystroke, with any modifiers that keystroke needs held down around it. Tab becomes a genuine TAB keypress; BEL ("\a") becomes CTRL+G.
• A control character the active layout cannot produce falls back to a Unicode packet.

Passing null throws ArgumentNullException; an empty string simulates nothing.

Modifier ordering

SimulateModifiedKeyStroke presses modifiers in the order given and releases them in reverse, so a key is never left stuck under another. Sequences are enumerated exactly once, so a lazily produced sequence cannot release different keys from the ones it pressed. A null sequence is treated as empty.

Things worth knowing

• UIPI. Input can only be injected into processes at an equal or lower integrity level. A simulation aimed at an elevated window silently does nothing unless your process is elevated too; the simulation methods throw when SendInput reports that nothing was inserted.
• Focus. SendInput targets whatever currently has keyboard focus. The library does not activate windows for you.
• Existing key state. SendInput does not reset the keyboard. If the user is holding a key when you inject input, the two combine. Check with IsKeyDownAsync when it matters.
• Mouse input is not simulated. MOUSEINPUT, MouseFlag and XButton are present for completeness of the interop surface.

Licence

See the repository for licence details.