retrieve a record using Dynamics 365 Web API with empty alternate key - dynamics-crm

Question

Problem
I'm trying to query records from Dynamics 365 using the Web API where a key attribute is null.
Approach
For testing purposes I created an entity with a string attribute, an integer attribute, and a decimal attribute. I then created an alternate key and put those three attributes in it, making this combination of attributes unique. I then created some records.
Querying the data using the Web API works as expected. I created a record with those values:
{
"my_string_key": "s1",
"my_integer_key": 1,
"my_decimal_key": 1.23
}
And query it like this:
/my_entities(my_string_key='s1',my_integer_key=1,my_decimal_key=1.23)
This returns the desired record.
However I can't get it to work when any of the key fields is empty, it always returns a 400 with message "Bad Request - Error in query syntax". Just for clarification: I purposely created records where one of the key attributes is empty, like this:
{
"my_integer_key": 1,
"my_decimal_key": 1.23
}
{
"my_string_key": "s1",
"my_decimal_key": 1.23
}
{
"my_string_key": "s1",
"my_integer_key": 1
}
Notice how each record is missing one of the key attributes, which effectively leaves it at null.
I tried using =null, =empty, ='', = and =Microsoft.OData.Core.ODataNullValue but nothing works. I tried to query them like this:
/my_entities(my_string_key=null,my_integer_key=1,my_decimal_key=1.23)
/my_entities(my_string_key='s1',my_integer_key=null,my_decimal_key=1.23)
/my_entities(my_string_key='s1',my_integer_key=1,my_decimal_key=null)
I also tried omitting the attribute with null in it, like this:
/my_entities(my_integer_key=1,my_decimal_key=1.23)
/my_entities(my_string_key='s1',my_decimal_key=1.23)
/my_entities(my_string_key='s1',my_integer_key=1)
None of this works. Can anyone provide a solution?
Final Words
I know that key attributes shouldn't be empty because that's not the point of key attributes. My scenario however requires to handle this specific case.
I also know that I could just use the $filter parameter, but I'd like a solution without having to resort to this "workaround". After all, it is a key and I'd like to treat it as one.

Answer 1

I think your efforts prove that key attributes cannot be empty. So, time for another approach.
Create a custom attribute and fill it with the combined values of the three key attributes. You can do this in a plugin registered in the pre operation stage of the Create and eventually Update messages of your entity.
Use the custom attribute as the key attribute.