Prevent Binding Loop with TextChanged-Event

Question

I have an Entry with implemented TextChanged-Event in XAML of my .NET MAUI App.

I wanted to prevent an empty Entry-Text and set „0“ instead when it‘s empty.

So, in TextChanged-Event I assigned my .Text to „0“ in case of string.IsNullOrEmptyCharacter(e.NewCalue). But now, in my model the bound value property is hit in Debugger in an endless-loop.

How would I solve this? Still wanted to make sure that the Text is updated by both, changes in the model as well the model, when Text is chanted/deleted.

How should I do this?

Answer 1

Since you have not posted your code, I'll give a generic answer.

The infinite loop occurs because your text-changed method is changing the value, thus firing text-changed again.

The solution is to make sure you "do nothing" if text-changed fires due to your programmatic change.

One way to do this, is to "do nothing", if your logic doesn't actually cause a change:

... MyTextChanged(string oldValue, string newValue)
{
    string alteredNewValue = newValue;

    ... // Logic that examines newValue, MAYBE comes up with a different value.

    // Avoids infinite loop, in case above logic tries to set same value again
    if (alteredNewValue == newValue)
        return;   // DON'T set the property again!

    // CAUTION: POTENTIAL INFINITE LOOP.
    MyTextProperty = alteredNewValue;
}

---

ANOTHER POSSIBLE FIX

Maybe there is a lurking issue if the property is set again during the TextChanged handler. If so, a simpler fix is to queue the property setting, so it happens after Maui has completed its changed processing:

...
Dispatcher.Dispatch(() => MyTextProperty = alteredNewValue);