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How to use logical IF with string function in Microsoft flow?

I built a flow to abstract a GUID from email body when new emails come in. The email body could contain:





I have built the following expression to extract the GUID


if(greater(indexof(body('Html_to_text'), '***KeyEnd'), 1),
substring(body('Html_to_text'), Add(indexof(body('Html_to_text'), 'KeyStart***'), 11), 36),
substring(body('Html_to_text'), 0, 36))


For the second case, it works. For the first case, it always returns "index out of range" in the substring. Does anyone know why?

Community Support Team
Community Support Team

Re: How to use logical IF with string function in Microsoft flow?

Hi @Gaolai,


Could you please share a screenshot of your flow's configuration?


The issue is confirmed on my side, I think this issue is related to the second parameter within your if() function. But when I add the following formula within a separated "Compose" action, the "Compose" action works well when the email body contains 3932FB4C-0DF5-11E8-A5C3-7804C4623542:





I afraid that this is issue is related to the if() function. In addition, you could consider take a try with the the following workaround as an alternative way:

  • Add a "When a new email arrives" trigger.
  • Add a "Html to text" action, Content field set to Body dynamic content of the trigger.
  • Add a Condition, click "Edit in advanced mode", type the following formula:
@greater(indexof(body('Html_to_text'), '***KeyEnd'), 1)
  • Within "If/yes" branch of Condition, add a "Compose" action, Inputs set to following formula:
  • Within "If/no" branch of Condition, add a "Compose 2" action, Inputs set to following formula:

Image reference:14.JPG

The flow works successfully as below:15.JPGBest regards,




Community Support Team _ Kris Dai
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
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Re: How to use logical IF with string function in Microsoft flow?

Thanks for your reply. I actually found out where the problem came from, the If operation will evaluate both parameter 2 and 3 no matter if the parameter 1 is true or false.

Level: Powered On

Re: How to use logical IF with string function in Microsoft flow?

Thanks @v-xida-msft this fixed my si,milar issue, but is there somewhere I can vote to get the if statement to not require this workaround. 

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