# Data Type parameters in expressions

**URL:** <https://forum.inductiveautomation.com/t/data-type-parameters-in-expressions/12320>\
**Category:** Ignition\
**Created:** [November 2, 2016, 2:02pm UTC](https://forum.inductiveautomation.com/t/data-type-parameters-in-expressions/12320 "2016-11-02T14:02:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![scicco](https://avatars.discourse-cdn.com/v4/letter/s/e0b2c6/32.png) [@scicco](https://forum.inductiveautomation.com/u/scicco)\
**Post date:** [November 2, 2016, 2:02pm UTC](https://forum.inductiveautomation.com/t/data-type-parameters-in-expressions/12320/1 "2016-11-02T14:02:03Z")

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Hello,

I’m trying to use a data type parameter in an expression tag and am getting the following error on the tag diagnostic:

“Error configuring tag for execution. Error: Syntax Error on Token: ‘End of Expression’ (Line 0, Char 0)”

I have no problem using a parameter reference in the Value field of a memory tag or in the SQL Query of a query tag. Not sure if this is a bug or if I’m missing something obvious.

The documentation says the following tag properties can reference parameters:

[ul]  
Value (for string data type only)  
OPC Server  
OPC Item Path  
Tooltip  
Documentation  
Expression/SQL Query  
Bindable Alarm Properties (Note: you can bind a property directly to the parameter, or use parameters in the binding expression, or directly in string property values)[/ul]

The attached PDF has screenshots of a test data type and instance that hopefully shows what I’m talking about.

[attachment=0]Data Type.pdf[/attachment]  
Thanks,  
Steve

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [November 2, 2016, 4:41pm UTC](https://forum.inductiveautomation.com/t/data-type-parameters-in-expressions/12320/2 "2016-11-02T16:41:49Z")

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If I recall correctly, parameters are processed before other syntax analysis by string substitution. So your empty string parm1 is being substituted, then treated as an expression, but it’s empty. Try adding quotes around the whole thing.

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<div class="post-metadata">

**Author:** ![scicco](https://avatars.discourse-cdn.com/v4/letter/s/e0b2c6/32.png) [@scicco](https://forum.inductiveautomation.com/u/scicco)\
**Post date:** [November 2, 2016, 4:47pm UTC](https://forum.inductiveautomation.com/t/data-type-parameters-in-expressions/12320/3 "2016-11-02T16:47:16Z")

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That did it - thank you.

I had tried toString({param1}) and when that didn’t work I guess I bypassed the obvious. Appreciate the help -