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How to detect when arrow key down is pressed / C# WPF

I'm working with WPF C# app, and I need to implement some action when arrow key down on keyboard is pressed, for example:
private void Window_KeyDown(object sender, KeyEventArgs e)
{
// Here I gotta check is that arrow key down which invoked this event.. then call a method
DoSomething();
}
I simply can not figure out in wpf how to detect a arrow key down ..
Any kind of help would be great!
Thanks !

The KeyEventArgs hold information about the pressed key in the KeyEventArgs.Key property and so you can check for the down arrow key by checking if e.Key is equal to Key.Down, which is the enumeration value for the arrow down key.
private void Window_OnKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Down) // The Arrow-Down key
{
DoSomething();
}
}

switch (e.Key)
{
case Key.Up:
break;
case Key.Down:
break;
case Key.Left:
break;
case Key.Right:
break;
default:
break;
}

C# Detect when key gets pressed and trigger a button

So I'm trying to make a simple calculator. The user can only input the numbers by the buttons on the form or by the numpad. This is the code I have:
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
string key = "";
switch (e.KeyCode)
{
case (Keys.NumPad1):
key = "1";
break;
case (Keys.NumPad2):
key = "2";
break;
default:
break;
}
txt_string.Text = txt_string.Text + key;
}
If I make a breakpoint on the KeyDown function and press the Numpad keys (and every other keys) the program doesnt even comes to that breakpoint.
Do I have to change something on my Form to detect the Keys?

You'll need to set KeyPreview to true (property on the form). Also, I would advise against trying to debug the behaviour - because you may affect the behaviour you're testing (Debug.WriteLine()) is your friend here.

Just to point out that many keyboard doesnt have numpad. You can check if the key is a integer.
void Form1_KeyDown(object sender, KeyPressEventArgs e)
{
if (char.IsDigit(e.KeyChar))
{
txt_string.Text += e.KeyChar;
}
}
This is more a Code Review than a solution though.

Change textBox.text to any key pressed

I'm trying to when a user presses a key in the textBox the textBox will show the key the user pressed so i can save it as a variable and use it elsewhere.
Right now i have this and this works
private void textBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
if(e.Key == Key.A)
{
textBox.Text = "A";
}
}
But it's limited to the A key is there any way to make it any key?

You can convert the KeyEventArgs e.KeyCode to a char.
private void textBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
Char ch = (Char)e.KeyCode;
textBox.Text = ch.ToString();
}
EDIT: Forgot this is WPF which doesn't support KeyEventArgs.KeyCode
private void textBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
textBox.Text = e.Key.ToString();
}
This will give you the things like CapsLock and Shift etc, but, in the
case of the alphanumeric keys, it won't be able to tell you the state
of shift etc. at the time, so you'll have to figure that out yourself.
The second alternative is to use the TextInput event instead, where
e.Text will contain the actual text entered. This will give you the
correct character for alphanumeric keys, but it won't give you control
characters.
Reference: https://stackoverflow.com/a/486967/6138713

Handling arrow key events on a winform textbox without overriding

I have a situation where I'm provided with a WinForms TextBox instance which I want to attach autocomplete functionality to.
I've got the autocomplete (string matching + dropdown) all figured out and it works reliable so far.
What is the ability to navigate the dropdown with the keyboard (as is the norm with this sort of UI).
The natural solution would be to handle KeyDown (or somesuch) event for the textbox and moving the selection in the dropdown accordingly.
However, it happens that to do this, you need to override the IsInputKey() event to allow capture of arrow key events. The alternative is to override ProcessCmdKey() and handle the event there. The problem with these two is that I cannot override anything since I can't replace the textbox instance.
Edit: Let's assume I have the code below:
void _textBox_KeyDown(object sender, KeyEventArgs e)
{
if (_dropdown.Visible)
{
// TODO The stuff below fails because we need to either handle ProcessCmdKey or override IsInputKey
switch (e.KeyCode)
{
case Keys.Tab:
{
// click selected item
_dropdown.Items[GetSelectedItemIndex()].PerformClick();
break;
}
case Keys.Down:
{
// select next (or first) item
int i = GetSelectedItemIndex() + 1;
if (i >= _dropdown.Items.Count) i = 0;
_dropdown.Items[i].Select();
break;
}
case Keys.Up:
{
// select previous (or last) item
int i = GetSelectedItemIndex() - 1;
if (i < 0) i = _dropdown.Items.Count - 1;
_dropdown.Items[i].Select();
break;
}
}
}
}
Them problem with the code above is that it is never called. The event is never triggered for arrow keys. More info: Up, Down, Left and Right arrow keys do not trigger KeyDown event

I hope i haven't missunderstood you, but is this a solution:
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Down)
{
// Place logic for textbox here
}
}
I'd use a KeyDown event on the form and then compare the keycode with the Keys.Down keycode
Not working
see here: Up, Down, Left and Right arrow keys do not trigger KeyDown event

I may not be understanding your question entirely, but wouldn't an approach like this work?
private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
comboBox1.Text = //results of your matching algorithm.
}
private void textBox1_Validated(object sender, EventArgs e)
{
textBox1.Text = (string) comboBox1.Text;
}

How to record typing in C# (keyListener)

I want to write a simple text to speech program.
First, I want to make the program play only the written symbol. For example, if I type 'a' I want the program to say 'a' (I have recorded all of them), so when I type a word, it should spell it.
However, I am a beginner in C# and .Net and don't how to make the program understand the text I type. For example, in java I heard that there is a keyListener class, but I don't know which class should I use. I looked on MSDN but couldn't find it.
Which class or function should I use to listen to typed keys?

I suppose you are planning to use Windows Forms to achieve this.
The solution would be pretty simple. These events include MouseDown, MouseUp, MouseMove, MouseEnter, MouseLeave, MouseHover, KeyPress, KeyDown, and KeyUp. Each control has these events exposed. You just need to subscribe to it.
Please refer to this
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.keydown.aspx
There would be a little bit of logic to find whether a complete word has been typed or not. A simple soultion would be , when space has been pressed, you can assume a word has been completed. Its very crude logic, as the user may have typed in wrong spelling and want hit backspace and correct the spelling. You may want to add lag to it.

If you are using Visual Studio like every other C# developer here is a more detailed code example:
Create a Windows Form and go to the [Design].
Select its properties (RMB=>properties), navigate to Events and double click LMB on KeyDown
VS will create and bind the event for you
Handle the KeyEventArgs depending on its value.
Example:
private void NewDialog_KeyDown(object sender, KeyEventArgs e)
{
switch (e.KeyData)
{
case Keys.A:
{
MethodToOutputSound(AEnum);
break;
}
case Keys.B:
{
MethodToOutputSound(BEnum);
break;
}
case Keys.F11:
{
DifferentMethod();
break;
}
case Keys.Escape:
{
this.Close();
break;
}
default:
{
break;
}
}
}
Or use a lot of ifs
private void NewDialog_KeyDown(object sender, KeyEventArgs e)
{
if(e.KeyData == Keys.A)
{
MethodToOutputSound(AEnum);
}
if(e.KeyData == Keys.B)
{
MethodToOutputSound(BEnum);
}
...
}

Create a Windows Form with a TextBox in it. Handle the KeyPress event - that will give you the actual character that the user types. KeyDown and KeyUp won't help you.
You need to check the KeyChar property. Like this:
void MyEventHandler(object sender, KeyPressEventArgs e) {
// Do stuff depending on the value of e.KeyChar
}

private void button1_Click_1(object sender, EventArgs e)
{
string word = textBox1.Text;
foreach (char i in word)
{
switch (i)
{
case 'a':
case 'A': { // play sound a
break;
}
default:
{
// play no sound
break;
}
}
}
}