C# – Textbox convert sent key : Alt + Enter -> Enter

ctextboxwpf

I'd like to be able to modify the behaviour of the wpf textbox without the need of implementing a new class.

I want an Excel like enter / Alt+Enter behavior, when the user hits "Enter" the textbox is validated (movefocus …), but when he hits "ALT+Enter", the textbox has to add a new line (my textbox supports multiline : AcceptsReturn is true).

I've tried (in the textbox PreviewKeyDown event):
– Raising to construct a KeyEventArgs and a TextCompositionEventArgs following this link : How can I programmatically generate keypress events in C#?
– I've tried SendKeys.SendWait("{ENTER}") but it sends many new line commands

Is there a way to do this ?

Thank you

    private void m_MeasurementName_PreviewKeyDown(object sender, KeyEventArgs e)
    {
        var tb = (sender as TextBox);

        if (Keyboard.Modifiers == ModifierKeys.Alt && Keyboard.IsKeyDown(Key.Enter))
        {
            // 1st try
            var key = "\n\r";
            var routedEvent = Keyboard.KeyDownEvent;
            tb.RaiseEvent(new TextCompositionEventArgs(InputManager.Current.PrimaryKeyboardDevice, new TextComposition(InputManager.Current, tb, key)) { RoutedEvent = routedEvent });

            // 2nd
            var key = Key.Enter;
            var routedEvent = TextCompositionManager.TextInputEvent;
            tb.RaiseEvent(new KeyEventArgs(Keyboard.PrimaryDevice, PresentationSource.FromVisual(tb), 0, key) { RoutedEvent = routedEvent });

            // 3rd
            System.Windows.Forms.SendKeys.SendWait("{ENTER}");

            // 4th Strangely works but not ... you know
            MessageBox.Show("ALT+ENTER");

            e.Handled = true;
        }
        else if (Keyboard.IsKeyDown(Key.Enter))
        {
            tb.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
            e.Handled = true;
        }
    }

Best Answer

If the user presses Alt+Enter, simply add a new line onto the existing TextBox.Text. If they hit just Enter, trigger an UpdateSource on the Text Binding

private void m_MeasurementName_PreviewKeyDown(object sender, KeyEventArgs e)
{
    var tb = (sender as TextBox);

    if (Keyboard.Modifiers == ModifierKeys.Alt && Keyboard.IsKeyDown(Key.Enter))
    {
        tb.Text += "\r\n";
        tb.SelectionStart = tb.Text.Length;

        e.Handled = true;
    }
    else if (Keyboard.IsKeyDown(Key.Enter))
    {
        var textBinding = BindingOperations.GetBindingExpression(
            tb, TextBox.TextProperty);

        if (textBinding != null)
            textBinding.UpdateSource();

        e.Handled = true;
    }
}

For the NewLine to work, make sure AcceptsReturn="True" on your TextBox

Original Answer

In .NET it's rather ugly (until 4 or above):

StatusEnum MyStatus = (StatusEnum) Enum.Parse(typeof(StatusEnum), "Active", true);

I tend to simplify this with:

public static T ParseEnum<T>(string value)
{
    return (T) Enum.Parse(typeof(T), value, true);
}

Then I can do:

StatusEnum MyStatus = EnumUtil.ParseEnum<StatusEnum>("Active");

One option suggested in the comments is to add an extension, which is simple enough:

public static T ToEnum<T>(this string value)
{
    return (T) Enum.Parse(typeof(T), value, true);
}

StatusEnum MyStatus = "Active".ToEnum<StatusEnum>();

Finally, you may want to have a default enum to use if the string cannot be parsed:

public static T ToEnum<T>(this string value, T defaultValue) 
{
    if (string.IsNullOrEmpty(value))
    {
        return defaultValue;
    }

    T result;
    return Enum.TryParse<T>(value, true, out result) ? result : defaultValue;
}

Which makes this the call:

StatusEnum MyStatus = "Active".ToEnum(StatusEnum.None);

However, I would be careful adding an extension method like this to string as (without namespace control) it will appear on all instances of string whether they hold an enum or not (so 1234.ToString().ToEnum(StatusEnum.None) would be valid but nonsensical) . It's often be best to avoid cluttering Microsoft's core classes with extra methods that only apply in very specific contexts unless your entire development team has a very good understanding of what those extensions do.

C# – How to convert a byte array to a hexadecimal string, and vice versa

You can use Convert.ToHexString starting with .NET 5.
There's also a method for the reverse operation: Convert.FromHexString.

For older versions of .NET you can either use:

public static string ByteArrayToString(byte[] ba)
{
  StringBuilder hex = new StringBuilder(ba.Length * 2);
  foreach (byte b in ba)
    hex.AppendFormat("{0:x2}", b);
  return hex.ToString();
}

or:

public static string ByteArrayToString(byte[] ba)
{
  return BitConverter.ToString(ba).Replace("-","");
}

There are even more variants of doing it, for example here.

The reverse conversion would go like this:

public static byte[] StringToByteArray(String hex)
{
  int NumberChars = hex.Length;
  byte[] bytes = new byte[NumberChars / 2];
  for (int i = 0; i < NumberChars; i += 2)
    bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
  return bytes;
}

Using Substring is the best option in combination with Convert.ToByte. See this answer for more information. If you need better performance, you must avoid Convert.ToByte before you can drop SubString.

Best Answer

Related Solutions

C# – Convert a string to an enum in C#

Original Answer

C# – How to convert a byte array to a hexadecimal string, and vice versa

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