Support nullable (alternate) keys in ODataPathQueryBuilder

[Xriuk]

Related: OData/odata.net#3415

Currently if I have a nullable property (like int?) used in an alternate key ODataPathQueryBuilder throws an exception when processing the generated KeySegment (with an int constant value):

System.InvalidOperationException: The binary operator Equal is not defined for the types 'System.Nullable`1[System.Int32]' and 'System.Int32'.
   at System.Linq.Expressions.Expression.GetEqualityComparisonOperator(ExpressionType binaryType, String opName, Expression left, Expression right, Boolean liftToNull)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at ...\ODataPathQueryBuilder.cs:line 69
...

Replacing:

WebApi/src/Microsoft.AspNet.OData.Shared/Query/ODataPathQueryBuilder.cs

Lines 68 to 71 in 1b8f45e

	IEnumerable<BinaryExpression> conditions = keySegment.Keys.Select(kvp =>
	Expression.Equal(
	Expression.Property(filterParam, kvp.Key),
	Expression.Constant(kvp.Value)));

With:

IEnumerable<BinaryExpression> conditions = keySegment.Keys.Select(kvp => {
	Expression prop = Expression.Property(filterParam, kvp.Key);
	Expression cons = Expression.Constant(kvp.Value);
	if (prop.Type != cons.Type)
		cons = Expression.Convert(cons, prop.Type);
	return Expression.Equal(prop, cons);
});

Seems to solve the issue

[habbes]

Hello @Xriuk, would you be open to contributing a PR to address this?

[Xriuk]

@habbes sorry for the late response, it seems I cannot contribute until the related issue is solved, nullable keys are not supported in odata.net yet, so I cannot run the appropriate unit tests