Question Why is a variable declared for text not the same as the property for the text?

[Thequazi]

Question in long form:
When I have this:

Dim input As String = Textbox1.text
Dim output As String = Textbox2.text
If input = 10 then output = "X"

I get no errors but it also doesn't change the text in textboxt2 to X

However, when I have this:

Dim input As String = Textbox1.text
If input = 10 then textbox2.text = "X"

It changes the text just fine.

 

[TheAppGuy]

Hi,

Dim output as string = Textbox2.text is not a pointer assignment, it is by Val(ue) not by Ref(erence), your later example sets the property directly.

 

[jmcilhinney]

Hi,

Dim output as string = Textbox2.text is not a pointer assignment, it is by Val(ue) not by Ref(erence), your later example sets the property directly.

That's not completely correct. String is a class, i.e. a reference type, so after this line:

Dim output As String = TextBox2.Text

'output' actually does refer to the same String object as TextBox2.Text. A reference is not a pointer though. This line:

If input = 10 then output = "X"

replaces the reference stored in the variable to a different reference, so 'output' now refers to a different String object.

String is a bit special as far as classes go anyway, in that instances are immutable, i.e. cannot be changed, so even if you wanted to modify the original object, you couldn't.