williamlove
Member
I'm inquiring about what happens when a VB program writes a null to the value in a string tag in the Logix program called MyString. I am using "null" to mean precisely what it is in a VB program.
Suppose I also have a second tag in my Logix program called BlankString that contains '' (two back to back single quotes which I get when I backspace everything out of the tag in tag monitor). This tag is never touched by the VB program.
My goal is that at specified times the VB programmer will write a blank string to MyString so that the instruction EQU MyString BlankString yields a true.
Is there any difference between the so called null value and a blank string? I have heard that there is, and want to understand it better so I can tell the VB programmer more. Let me ask more specifically, if the VB programmer writes the null value to MyString will that populate the tag with something other than ''?
[I will respectfully ask that you answer only if you are pretty sure about your answer because we already have a lot of educated guesses and discussion.]
Suppose I also have a second tag in my Logix program called BlankString that contains '' (two back to back single quotes which I get when I backspace everything out of the tag in tag monitor). This tag is never touched by the VB program.
My goal is that at specified times the VB programmer will write a blank string to MyString so that the instruction EQU MyString BlankString yields a true.
Is there any difference between the so called null value and a blank string? I have heard that there is, and want to understand it better so I can tell the VB programmer more. Let me ask more specifically, if the VB programmer writes the null value to MyString will that populate the tag with something other than ''?
[I will respectfully ask that you answer only if you are pretty sure about your answer because we already have a lot of educated guesses and discussion.]