Paste Event in a WPF TextBox

Question

I have created a custom control inheriting TextBox. This custom control is a numeric TextBox, only supporting numbers.

I am using OnP

Answer 1

This might not be the exact answer your looking for but here is how to handle pasted text (this also works if user pasted using a the context menu):

InitializeComponent();

                // "DescriptionTextBox" is a TextBox
                DataObject.AddPastingHandler(DescriptionTextBox, OnDescriptionPaste);

private void OnDescriptionPaste(object sender, DataObjectPastingEventArgs e)
        {
            if (!e.SourceDataObject.GetDataPresent(DataFormats.UnicodeText, true))
                return;

            var pastedText = e.SourceDataObject.GetData(DataFormats.UnicodeText) as string;
            if (string.IsNullOrEmpty(pastedText))
                return;

            var txtBox = (TextBox) sender;

            var before = ""; //Text before pasted text
            var after = txtBox.Text; //Text after pasted text

            //Get before and after text
            if (txtBox.CaretIndex > 0)
            {
                before = txtBox.Text.Substring(0, txtBox.CaretIndex);
                after = txtBox.Text.Substring(txtBox.CaretIndex);
            }

            //Do custom logic for handling the pasted text.
            //Split sentences ending with . into new line.
            var parts = pastedText.Split(new []{'.'}, StringSplitOptions.RemoveEmptyEntries);
            if (parts.Length > 1)
            {
                pastedText = parts.Select(x => x.Trim()).ToArray().ToStringX(".\r\n");
                pastedText += ".";
            }

            var newCaretIndex = before.Length + pastedText.Length;

            e.CancelCommand(); //Cancels the paste, we do it manually
            txtBox.Text = $"{before}{pastedText}{after}"; //Set new text
            txtBox.CaretIndex = newCaretIndex; //Set new caret index
        }

For handling backspace use PreviewKeyDown event.