support select of same parameter

Author: Ihar Yakimush

SolrNet.IntegrationOData/Controllers/ValuesController.cs

@@ -33,6 +33,7 @@ public IActionResult Get()
                 "/api/values/1?$filter=Popularity eq null",
                 "/api/values/1?$filter=Categories/any(c: c eq 'electronics')",
                 "/api/values/2?$select=Id,Price,Categories",
+                "/api/values/3?$select=Id,Price,Categories",
             });
         }
 
@@ -71,5 +72,14 @@ public ActionResult<string> Get2(ODataQueryOptions odata)
 
             return this.Ok(query.OData().ApplyQueryOptions(odata).ToJson());
         }
+
+        // GET api/values/5
+        [HttpGet("3")]
+        public ActionResult<string> Get3(ODataQueryOptions odata)
+        {
+            IQueryable<Product> query = this.Solr.AsQueryable();
+
+            return this.Ok(query.OData().ApplyQueryOptions(odata).ToJson());
+        }
     }
 }

SolrNet.Linq.IntegrationTests/DerivedProduct.cs

@@ -0,0 +1,7 @@
+namespace SolrNet.Linq.IntegrationTests
+{
+    public class DerivedProduct : Product
+    {
+        public string Id2 { get; set; }
+    }
+}

SolrNet.Linq.IntegrationTests/SelectTests.cs

@@ -138,6 +138,33 @@ public void AnonymousClassSolrResult()
             Assert.True(t1.NumFound > 0);
         }
 
+        [Fact]
+        public void SelectDerivedClassCast()
+        {
+            IQueryable<DerivedProduct> derivedProducts = Product.SolrOperations.Value.AsQueryable().Where(p => p.Id != null)
+                .Select(p => new DerivedProduct{Id2 = p.Id}).Where(p => p.Id2 != null);
+
+            IQueryable<Product> q2 = derivedProducts.Cast<Product>();
+
+            var t1 = q2.ToSolrQueryResults();
+
+            Assert.NotNull(t1);
+            Assert.NotNull(t1[0].Id);
+            Assert.True(t1.NumFound > 0);
+        }
+
+        [Fact]
+        public void SelectSameParameter()
+        {
+            var t1 = Product.SolrOperations.Value.AsQueryable().Where(p => p.Id != null)
+                .Select(p => p).Where(p => p.Id != null)
+                .ToSolrQueryResults();
+
+            Assert.NotNull(t1);
+            Assert.NotNull(t1[0].Id);
+            Assert.True(t1.NumFound > 0);
+        }
+
         [Fact]
         public void MultipleSelects()
         {

SolrNet.Linq/Expressions/SelectMethod.cs

@@ -9,7 +9,7 @@ namespace SolrNet.Linq.Expressions
     public static class SelectMethod
     {
         public const string Select = nameof(Queryable.Select);
-        public static bool TryVisitSelect(this MethodCallExpression node, SelectExpressionsCollection options, MemberContext context, out SelectContext newContext)
+        public static bool TryVisitSelect(this MethodCallExpression node, SelectExpressionsCollection options, MemberContext context, out MemberContext newContext)
         {
             newContext = null;
             bool result = node.Method.DeclaringType == typeof(Queryable) && node.Method.Name == Select;
@@ -31,14 +31,20 @@ public static bool TryVisitSelect(this MethodCallExpression node, SelectExpressi
                         newContext = new SelectContext(memberInit, context);
                     }
 
+                    if (lambda.Body is ParameterExpression)
+                    {
+                        newContext = context;
+                        return result;
+                    }
+
                     if (newContext != null)
                     {
                         options.Fields.Clear();
                         SelectFieldsVisitor visitor = new SelectFieldsVisitor(context, options);
                         visitor.Visit(lambda.Body);                                                
 
                         return result;
-                    }
+                    }                    
                 }
 
                 throw new InvalidOperationException($"Unable to translate '{Select}' method.");

SolrNet.Linq/Impl/ExecuterExtensions.cs

@@ -14,7 +14,10 @@ namespace SolrNet.Linq.Impl
 {
     internal static class ExecuterExtensions
     {
-        public static IExecuter<TNew> ChangeType<TNew, TOld>(this IExecuter<TOld> executer, MethodCallExpression selectExpression, SelectExpressionsCollection selectExpressionsCollection)
+        public static IExecuter<TNew> ChangeType<TNew, TOld>(
+            this IExecuter<TOld> executer, 
+            MethodCallExpression selectExpression, 
+            SelectExpressionsCollection selectExpressionsCollection)
         {
             if (executer == null) throw new ArgumentNullException(nameof(executer));
             if (selectExpression == null) throw new ArgumentNullException(nameof(selectExpression));

SolrNet.Linq/SolrOperationsExtensions.cs

@@ -20,7 +20,9 @@ public static IQueryable<T> AsQueryable<T>(this ISolrBasicReadOnlyOperations<T>
 
         public static SolrQueryResults<T> ToSolrQueryResults<T>(this IQueryable<T> queryable)
         {
-            return (SolrQueryResults<T>)queryable.Provider.Execute(queryable.Expression);
+            object execute = queryable.Provider.Execute(queryable.Expression);
+
+            return (SolrQueryResults<T>)execute;
         }
 
         public static Task<SolrQueryResults<T>> ToSolrQueryResultsAsync<T>(this IQueryable<T> queryable)