Assign: Value cannot be null. (Parameter 'source') List Error

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1

Hi,

I declared a list variable and then use linq query to filter the data table. but when ever the condition does not satisy it returns empty or null value and throws error. What is the workaround to avoid this condition?

Assign: Value cannot be null. (Parameter ‘source’)

The image shows a sequence of two Assign activities in a workflow, where the variable is initially set to a new list of strings, and then to . (Captioned by AI)
The image shows a sequence of two Assign activities in a workflow, where the variable is initially set to a new list of strings, and then to . (Captioned by AI)698×260 20.2 KB

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@dutta.marina

Before doing select…use .Count and check the count >0 using if condition…if yes then assign if no then that means no value is returned

Cheers

3

Hi @dutta.marina ,

Use if condition and check if filtered data Row Count > 0, if yes then assign else you can clone the datatable to return empty values
e.g.
If(YourDT.AsEnumerable().Where(Function(row) row(“Col1”).ToString.Equals(“Value”)).Count>0,YourDT.AsEnumerable().Where(Function(row) row(“Col1”).ToString.Equals(“Value”)).CopytoDataTable,YourDT.Clone)

The image shows an assignment statement in a workflow, where a DataTable "YourDT" is being filtered based on a condition and reassigned using a conditional expression. (Captioned by AI)
The image shows an assignment statement in a workflow, where a DataTable "YourDT" is being filtered based on a condition and reassigned using a conditional expression. (Captioned by AI)903×235 52.7 KB

Thanks,
Rashmi

4

@Anil_G

If list is returning a valid object i can use above code , but here list itself null so i cannot chain the count function. Once it goes to else block ot throws same error

This image depicts a UiPath sequence workflow with an assignment activity followed by a conditional "If" activity that checks if the count of items in a list is greater than zero, executing different actions based on the condition's outcome. (Captioned by AI)
This image depicts a UiPath sequence workflow with an assignment activity followed by a conditional "If" activity that checks if the count of items in a list is greater than zero, executing different actions based on the condition's outcome. (Captioned by AI)694×639 39.8 KB

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@dutta.marina

Use this expression to check if it’s null or empty.

str_latestfile_link IsNot Nothing AndAlso str_latestfile_link.Count >0

Thanks,
Ashok :slightly_smiling_face:

6

@dutta.marina

the count to be done on dt.Asenuemrable.where(blah blah).count>0 then assign to list inside the then block …on else block do nothing

I understand list is where you are tryign to collect the data

cheers

1 Like
7

@dutta.marina

if resolved can you close this thread

else happy to help

cheers

8

@Anil_G

Done

The image shows a community moderator's suggestion on a coding forum, illustrating how to use a LINQ query to filter and count rows based on specific string conditions in the "FileName" field. (Captioned by AI)
The image shows a community moderator's suggestion on a coding forum, illustrating how to use a LINQ query to filter and count rows based on specific string conditions in the "FileName" field. (Captioned by AI)1732×1004 109 KB

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