Implement ignoring filter case-sensitivity

[Kebechet]

When we want to filter some string fields we would like to specify on BE when we call
queryOptions.Filter.ApplyTo option to ignore case-sensitivity of values so that with
word eq dog we can match records Dog, dog, DoG

It would probably make sense to specify this as a part of ApplyTo or in ODataQueryOptions that is used for filter's ApplyTo

Related discussions:

• Can i filter with case insensitive #633
• Remove case sensitivity from Filter for Odata #762
• https://learn.microsoft.com/en-us/answers/questions/1274766/is-filter-eq-case-sensitive-or-not

Are there any reasons this is not yet implemented?

Workoarounds:

• in the query use toLower or toUpper. E.g.
  • ?$filter=tolower(Name) eq 'john'
  • ?$filter=contains(tolower(Name),'john')
• in EF using a case-insensitive collation (ends with CI... on SQL Server, or NOCASE on SQLite)

[xuzhg]

@Kebechet ODL enables the key word case-insensitive, but not for the instance value.
I think OData spec can consider to introduce the case insensitive comparison.
But before that, you maybe get this by customizing the 'FilterBinder' besides the workarounds you listed.

Simple prototype:

1. Create a class derived from FilterBinder
2. Override the BindBinaryOperatorNode
3. implement your own case insensitive filter for your string scenario
4. for other scenarios, call the base.BindBinaryOperatorNode.

I haven't tested the above (maybe I will do something later) , let me know if you need more details.

[xuzhg]

@Kebechet Ok, I have a quick sample for your reference, please let me know if you have any questions. Thanks.