Control Source Error

[ameedoo3000]

Hi all
There was a problem selecting the data source with expression builder As shown in the pictures below.
Please explain why and solve the problem
Greetings
ِAhmed

 

[Tore Bleken]

Without studying too much, I notice that the IIF() statement misses a parameter, the "else" value. I haven't used this type in many years, but I seem to remember that the expressions also must be preceded by a =.

 

[TamarGranor]

Tore hit it on the nose. To specify something other than a field as the ControlSource in a grid, you need to precede the expression with =.

Tamar

 

[ameedoo3000]

Thanks a lot .. the problem has been solved

 

[Olaf Doschke]

No, a controlsource expression (other than simply a field) always needs to be enclosed with brackets, not preceded by a "=".
A controlsource is evaluating its value anyway, but this fails even with simple expressions and leads to the error. This is an old known misbehaviour of the controlsoure.
If you prefix an expression with "=" in the controlsource, you only cause a one time evaluation of that expression and the result has to be an expression you want as controlsource.
If you set controlsource to "=exam_1+exam_2" you would set it to whatever number and that won't work out at all, Tore, Tamar.

Bye, Olaf.

Olaf Doschke Software Engineering

https://www.doschke.name

 

[ameedoo3000]

thanks very much Olaf.

 

[Mike Lewis]

Regardless of the fact that the control source needs to be enclosed in parentheses or preceded by an equals, your actual expression is incorrect:

[tt]
IIF((table1.exam_1 + table1.exam_2) > 85, "Excellent")[/tt]

You need three arguments to IIF(): the condition, the "true" expression, and the "false" expression. So something like this would be better:

[tt]IIF((table1.exam_1 + table1.exam_2) > 85, "Excellent", "Other")[/tt]

Mike



__________________________________
Mike Lewis (Edinburgh, Scotland)

Visual FoxPro articles, tips and downloads

 

[Tore Bleken]

I already comment on that in my first reply.

 

[Olaf Doschke]

Well, you gave the wrong recommendation of preceding with "=", that's not the solution, also not setting the controlsource ="exam_1+exam_2"

Edit: I tried, this works, but then also exam_1+exam_2 as was initially done. Maybe the latest Hotfix finally fixed that, I'd still always use bracketing. In that case VFP never tells you controlsource "must be a variable reference".

Bye, Olaf.

Olaf Doschke Software Engineering

https://www.doschke.name

 

[Tore Bleken]

If you prefer to misunderstand, then that's your choice.

 

[Olaf Doschke]

I see Mikes post now. Sorry, Tore.

Bye, Olaf.

Olaf Doschke Software Engineering

https://www.doschke.name

 

[ameedoo3000]

Now everything is fine
thank you all