Filtering based on derived property Types in dynamic Linq

[chait-01]

Here is what to include in your request to make sure we implement a solution as quickly as possible.

1. Description

I am using dynamic lambda expression, and trying to filter records based on a derived type.

var expr1 = DynamicExpressionParser.ParseLambda<Settings, bool>(new ParsingConfig(), true, "c => (c.Applicability As WinApplicability).SKUs.Contains(@0)", result);

Here Appilicability is a property within Settings type, and WinApplicability is a derived type of Applicability. SKUs is a property within WinApplicability.

The above line of code fails with the below error. Any idea how to deal with this issue?

Exception

System.Linq.Dynamic.Core.Exceptions.ParseException: ')' or operator expected

If I try to use static lambda expression, I dont see any error, but result being variable, the code fails with

Expression<Func<Settings, bool>> expr2 = c => (c.Applicability as WinApplicability).SKUs.Contains(result);

since the variable "result" is not pre-computed

"Object reference not set to an instance of an object."
StackTrace = "   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()\r\n   at System.Linq.SystemCore_EnumerableDebugView`1.get_Items()"

[StefH]

#622

[StefH]

Hello @chait-01, in your example you use the as as the naming operator (giving a property a different name).

In your example here, you need this code:

var config = new ParsingConfig { ResolveTypesBySimpleName = true };
var expr1 = DynamicExpressionParser.ParseLambda<Settings, bool>(config, true, "As(Applicability, \"WinApplicability\").SKUs.Contains(@0)", result);

See also unit-test:
https://github.com/zzzprojects/System.Linq.Dynamic.Core/blob/master/test/System.Linq.Dynamic.Core.Tests/QueryableTests.Is%2COfType%2CAs%2CCast.cs#L181

Note that I'll also update the documentation on https://dynamic-linq.net/expression-language#is-and-as-examples

[StefH]

@chait-01
Explanation for

in your example you use the as as the naming operator (giving a property a different name).