Method to highlighting Text in TextBox is inconsistent

问题

Currently I am using this method to highlight text inside a TextBox, but it works just sometimes.

This code has to verify if there is contained a space in the entered text. If there is a space in the text the user should be warned, and then the text inside the TextBox has to be highlighted:

if (textBox.Text.Contains(" "))
{
    MessageBox.Show("Sorry, the value entered must not contain any spaces.", "Please enter a valid value", MessageBoxButton.OK, MessageBoxImage.Error);

    //Highlights incorrect text
    textBox.SelectionStart = 0;
    textBox.SelectionLength = textBox.Text.Length;
}

Why isn't this method working for me all the time and what can I do to fix it?

回答1:

It might be a problem when you are selecting length of textBox which has no focus in current moment.

Can you try to add check for focus?

if (textBox.Text.Contains(" "))
{
    MessageBox.Show("Sorry, the value entered must not contain any spaces.", "Please enter a valid value", MessageBoxButton.OK, MessageBoxImage.Error);

    if(!textBox.Focused)
    {
      textBox.Focus();
    }

    //Highlights incorrect text
    textBox.SelectionStart = 0;
    textBox.SelectionLength = textBox.Text.Length;
}

Also instead of current solution you can use textBox.SelectAll():

if (textBox.Text.Contains(" "))
{
    textBox.SelectAll();
    MessageBox.Show("Sorry, the value entered must not contain any spaces.", "Please enter a valid value", MessageBoxButton.OK, MessageBoxImage.Error);

}

来源：https://stackoverflow.com/questions/24394304/method-to-highlighting-text-in-textbox-is-inconsistent

标签

wpf

textbox