Logic for adding \ before every character in ADF parameter - azure-data-factory-2

Question

I have a requirement in ADF wherein i have a parameter which can contain following values AB or A or B
I want to update these values by appending \ in front of each character.
So the output should be as follows:
For AB - \A\B
For A - \A
How to append \ in front of every character irrespective of number of characters in a parameter?
Please note that we don't want to use DataFlow for this.

Answer 1

You cannot do this with the native expressions in ADF. Either call an Azure function to perform the work, or use SQL and a Lookup Activity to perform the task. You can put the following into a dynamic expression referencing the following as an example;
declare ##str nvarchar(max) = 'helloworld'; /* get value in dynamic expression '#{#pipeline().parameters.PARAMETER_NAME}'*/
declare ##strOut nvarchar(max) = '';
declare ##strlen int = len(##str);
declare ##i int = 1;
while ##i <= ##strlen
begin
set ##strOut += concat('\',SUBSTRING(##str,##i,1));
set ##i +=1;
end
select ##strOut [result];
Then fetch the result from the activity. e.g. #activity('Lookup1').output.firstRow.result
As seen below, note the UI is just adding the extra \ in the preview, (ADF rendering bug)
The dynamic expression in the Lookup Query parameter :