CODEWITHSUNDEEP
c#winformskeydown
Andy Stampor
Andy Stampor

Reputation: 688

How do I convert a "Keys" enum value to an "int" character in C#?

This seems like something that should be easy, but I am having a tough time figuring out what needs to happen here.

In the "KeyDown" eventhandler, if the "e.KeyValue" is a number, I want to treat it as a number and store it as an int. So, if I hit "8" on the number pad, I don't want "Numpad8" I want the int value 8 that I can add or subtract or whatever.

So, how do I convert from the KeyValue to an int?

Upvotes: 9

Views: 33006

Answers (12)

Ralph B.
Ralph B.

Reputation: 13

here is another way on how to get a usable value:

string key
if (((int)e.Key < 84 && (int)e.Key > 73) || ((int)e.Key < 44 && (int)e.Key > 33))
{
    key = ((int)e.Key - 4).ToString();
    key = key.Remove(0,1);
}

Alternative to what Carlos Ferreira posted.

Upvotes: 0

Carlos Ferreira
Carlos Ferreira

Reputation: 93

I used this 2 lines simple code:

string key = e.KeyCode.ToString();

if (key.Length > 1) key = key.Replace("NumPad", "").Replace("D", "");

Upvotes: 0

Tommi Forsstr&#246;m
Tommi Forsstr&#246;m

Reputation: 1467

I'd go with this solution:

int value = -1;
if (e.KeyValue >= ((int) Keys.NumPad0) && e.KeyValue <= ((int) Keys.NumPad9)) { // numpad
    value = e.KeyValue - ((int) Keys.NumPad0);
} else if (e.KeyValue >= ((int) Keys.D0) && e.KeyValue <= ((int) Keys.D9)) { // regular numbers
    value = e.KeyValue - ((int) Keys.D0);
}

...if the point was to get the numeric value of the label of they key that was punched in.

Upvotes: 17

THX-1138
THX-1138

Reputation: 21730

Facts: Keyboard has keys. Some keys represent numbers and some do not.

Problem (rephrased): Yield a numeric value represented by a key, if the key represents a number.

To solve the problem it is necessary to know which keys (out of set of all keys) represent numbers as well as exact numeric value each (number) key represents.

To my knowledge there is no an easy way to get such a mapping from the framework.

Note: The fact D0-D9 and NumPad0-NamPad9 are sequential in the Keys enum is accidental and relying on these values being ordered sequentially is unfounded.

So solution would be:

  1. Determine if given key represents a number.
  2. Return numeric value of the key if key represents a number.
private static readonly IDictionary<Keys, int> NumericKeys = 
    new Dictionary<Keys, int> {
        { Keys.D0, 0 },
        { Keys.D1, 1 },
        { Keys.D2, 2 },
        { Keys.D3, 3 },
        { Keys.D4, 4 },
        { Keys.D5, 5 },
        { Keys.D6, 6 },
        { Keys.D7, 7 },
        { Keys.D8, 8 },
        { Keys.D9, 9 },
        { Keys.NumPad0, 0 },
        { Keys.NumPad1, 1 },
        { Keys.NumPad2, 2 },
        { Keys.NumPad3, 3 },
        { Keys.NumPad4, 4 },
        { Keys.NumPad5, 5 },
        { Keys.NumPad6, 6 },
        { Keys.NumPad7, 7 },
        { Keys.NumPad8, 8 },
        { Keys.NumPad9, 9 }
   };

private int? GetKeyNumericValue(KeyEventArgs e) {
    if (NumericKeys.ContainsKey(e.KeyCode)) return NumericKeys[e.KeyCode];
    else return null;
}

Arguably, not the simplest solution, but the one that models the solution closely.

Upvotes: 5

John Fisher
John Fisher

Reputation: 22719

Something like this should work well: (Edited)

int keyVal = (int)e.KeyValue;
int value = -1;
if ((keyVal >= (int)Keys.D0 && keyVal <= (int)Keys.D9)
{
    value = (int)e.KeyValue - (int)Keys.D0;
}
else if (keyVal >= (int)Keys.NumPad0 && keyVal <= (int)Keys.NumPad9)
{
    value = (int)e.KeyValue - (int)Keys.NumPad0;
}

Upvotes: 5

salgo60
salgo60

Reputation: 967

Or create a extension method and call it like 

private void Form1_KeyDown(object sender, KeyEventArgs e)
{    
    int num = e.KeyValue.GetKeyValue();  
}

where the extension method is 

public static class MyExtensions
{
    public static int GetKeyValue(this int keyValue)
    {

        if (keyValue >= 48 && keyValue <= 57)
        {
            return keyValue - 48;
        }
        else if (keyValue >= 96 && keyValue <= 105)
        {
            return keyValue - 96;
        }
        else
        {
            return -1; // Not a number... do whatever...    }

        }
    }
}

Upvotes: 0

Robin Day
Robin Day

Reputation: 102478

The KeyValue represents the character code for the key that was pressed. In order to obtain its numerical valaue you should find the character for the key that was pressed, then parse it from a character to an integer.

Something like Convert.ToInt32(e.KeyCode.ToString())

Upvotes: 0

John Rasch
John Rasch

Reputation: 63445

This function will do what you want:

private int GetKeyValue(int keyValue)
{
    if (keyValue >= 48 && keyValue <= 57)
    {
        return keyValue - 48;
    }
    else if (keyValue >= 96 && keyValue <= 105)
    {
        return keyValue - 96;
    }
    else
    {
        return -1; // Not a number... do whatever...
    }
}

Call it like so:

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    int num = GetKeyValue(e.KeyValue);  
}

Upvotes: 1

Samuel
Samuel

Reputation: 38346

Could you just listen for the KeyPress event instead? It will give the character that was actually pressed.

Upvotes: 1

Adam Robinson
Adam Robinson

Reputation: 185643

If you want NUMERIC values, you'll have to create a switch(e.KeyCode) statement and evaluate the key and create your own int. There's no simple way to turn a Keys into a numeric value that represents the number on the key. The closest you could get might be the ASCII equivalent, which would still need to be translated.

Upvotes: 2

Jeremy
Jeremy

Reputation: 107

int i = (int)e.KeyValue;

Upvotes: -3

TheTXI
TheTXI

Reputation: 37885

Depending on how many keys you are keeping track of, the simplest method would be for you to create a select case (or switch statement in C# I guess?) that would check the value of your keydown and depending upon that value assign a value to an integer that is appropriate.

Upvotes: 2

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