Fold member access into conditional

Fixes dotnet#34589.

Author: ranma42

src/EFCore.InMemory/Query/Internal/InMemoryQueryableMethodTranslatingExpressionVisitor.cs

@@ -1146,6 +1146,16 @@ public Expression Expand(InMemoryQueryExpression queryExpression, Expression lam
 
         protected override Expression VisitMember(MemberExpression memberExpression)
         {
+            // Fold member access into conditional, i.e. transform
+            // (test ? expr1 : expr2).Member -> (test ? expr1.Member : expr2.Member)
+            if (memberExpression.Expression is ConditionalExpression cond) {
+                return Visit(Expression.Condition(
+                    cond.Test,
+                    Expression.MakeMemberAccess(cond.IfTrue, memberExpression.Member),
+                    Expression.MakeMemberAccess(cond.IfFalse, memberExpression.Member)
+                ));
+            }
+
             var innerExpression = Visit(memberExpression.Expression);
 
             return TryExpand(innerExpression, MemberIdentity.Create(memberExpression.Member))

src/EFCore.Relational/Query/RelationalSqlTranslatingExpressionVisitor.cs

@@ -631,6 +631,16 @@ protected override Expression VisitListInit(ListInitExpression listInitExpressio
     /// <inheritdoc />
     protected override Expression VisitMember(MemberExpression memberExpression)
     {
+        // Fold member access into conditional, i.e. transform
+        // (test ? expr1 : expr2).Member -> (test ? expr1.Member : expr2.Member)
+        if (memberExpression.Expression is ConditionalExpression cond) {
+            return Visit(Expression.Condition(
+                cond.Test,
+                Expression.MakeMemberAccess(cond.IfTrue, memberExpression.Member),
+                Expression.MakeMemberAccess(cond.IfFalse, memberExpression.Member)
+            ));
+        }
+
         var innerExpression = Visit(memberExpression.Expression);
 
         return TryBindMember(innerExpression, MemberIdentity.Create(memberExpression.Member), out var expression)