Variable as default value for Data Card doesn't refresh

[anotherlama]

Hello everyone!
I have an edit form that is displaying different monetary values. In order to show them in correct formating, I have set the default values to variables like "varCateringCost". The onchange property is then set to:

Set(varCateringCost;
Text(Value(DataCardValue1.Text);"[$-de-DE]€ ###.##0"))

This works absolutely fine with all cases except of one:

If I change from 200 to 300, eg, it correctly displays € 200 and then € 300.
However, I realized, if I completly delete the text inside the input field, it looks to the user as if it was blank, but it still patches the old value to the sharepoint list. I created a workaround:

Set(varCateringCost;
If(IsBlank(DataCardValue1.Text) || DataCardValue1.Text = "" || IsEmpty(DataCardValue1.Text);
Text(Value("0");"[$-de-DE]€ ###.##0");
Text(Value(DataCardValue1.Text);"[$-de-DE]€ ###.##0")))

This works fine the first time. For example, changing fom € 300 to empty, it is displaying € 0 and thus should also patch 0.
However, if I remove "€ 0" again, the field is just staying empty. I tested the value of the variable outside the data card. The value seems to be "€ 0". This however is not correctly displayed inside the data card. I assume, the variable varCateringCost, which is the default value for the datacardvalue1 field, is not refreshed properly. Does anyone have an idea what to do? I am absolutly open for different ways of solving this. The only thing I need is the correct submission of an empty or blank field to the sharepoint list. Thanks a lot in advance!

[Delid4ve]

Scrap the variables, reset it to how it was and put a label next to the input field with “€” in it,
If you want to be really clever you can put a rectangle around it all (position behind) to put a border around the whole lot so it appears as one box

[v-yutliu-msft]

Hi @anotherlama ,

I've made a similar test and met the same problem.

I've reported this issue to our product team. If there's any replay, I will leave  message here.

Firstly, I suggest you separate number and "$" like @Delid4ve  said. Then you could avoid the situation of not display "$".

Secondly, I suggest you not use variable to justify whether the textinput has value. Then you could avoid the default value becoming blank.

You could set this field's UpDate directly:

If(IsBlank(DataCardValue1.Text),0,Value(DataCardValue1.Text))

In this way, you could make sure that the update value is right.

Best regards,

[anotherlama]

hi @Delid4ve and @v-yutliu-msft !
thanks a lot for your response! 
However, the currency formatting with "###.###" and the currency sign "€"  need to be included. Especially the dot between the thousands digit and the hundreds digit. If I continue as suggest, I think the formatting is not happening anymore. Is that correct? Any ideas what else I could do?