@PowerUser19
You don't do this in Power Apps:
//don't do this to try to set DataCardValue16.Value
DataCardValue16.Value="Firstname Lastname"
//don't try to set DataCardValue16.Value directly in a formula.
//the only reason to say
//DataCardValue16.Value="Firstname Lastname"
//is if you want to check if DataCardValue16.Value is equal to "Firstname Lastname" - but this will not set the value of the data card.
You do not set the "Property.Value" directly in Power Apps using an equal sign.
= means "check if the left side is equal to the right side" - it never sets anything.
Whenever you want to say Something.Value = "Something else" to set a value of something - remember not to do that in Power Apps - you only do that if you want to compare if Something.Value is equal to "Something else".
You should approach this another way in Power Apps.
"Control.Value" of something can be accessed from elsewhere, but it is not to be "set" directly in the way you are attempting, in Power Apps.
To achieve what you want where something has a default value,
just use the Default property of the control.
For example, Drop down control has a Default property which could be used for this purpose.
Drop down control key properties - docs.microsoft.com
When the Default property is used, suppose on a Drop down control called Dropdown1 - if the user does not change anything in Dropdown1, then Dropdown1.Selected.Value - when accessed from elsewhere, should match what's in the Default property of Dropdown1.
For a Combo box control, it would be DefaultSelectedItems
Key properties of Combo box controls - docs.microsoft.com
Check if it helps @PowerUser19
