Put the value from a StringEdit to a variable for a parameters in a query

Hi i am new in Dynamics Ax.

I try to extract the value from a StringEdit  to use in a Query with X++ in a click event.

I know how to do for example in VB but i cant find  the paralel method in X++.

for example:

i have  a form with a TextBox1

and take the text value in a variable A

then i declare a sql statement like select JournalId from InventJournal where JournalId == variable A

in VB be like:

variable A = Me.TextBox1.Text

i very gratefull if can oriented with an example or some resources to find the correct method.