#41 implement support for min

Author: kccarter76

SubSonic.Tests/DAL/ExtensionMethod/ExtensionMethodTests.cs

@@ -10,10 +10,24 @@
 
 namespace SubSonic.Tests.DAL.ExtensionMethod
 {
+    using Extensions.Test;
+
     [TestFixture]
     public class ExtensionMethodTests
         : BaseTestFixture
     {
+        protected override void SetSelectBehaviors()
+        {
+            base.SetSelectBehaviors();
+
+            string
+                person_min = @"SELECT MIN([T1].[ID])
+FROM [dbo].[Person] AS [T1]";
+
+            Context.Database.Instance.AddCommandBehavior(person_min, cmd => People.Min(x => x.ID));
+        }
+
+
         [Test]
         public void TheCountMethodIsSupported()
         {
@@ -25,5 +39,11 @@ public void TheLongCountMethodIsSupported()
         {
             Context.People.LongCount().Should().BeGreaterThan(0).And.IsOfType<long>();
         }
+
+        [Test]
+        public void TheMinMethodIsSupported()
+        {
+            Context.People.Min(x => x.ID).Should().Be(1);
+        }
     }
 }

SubSonic.Tests/DAL/SUT/BaseTestFixture.cs

@@ -76,11 +76,11 @@ public virtual void SetupTestFixture()
 
             Renters = new List<Renter>()
             {
-                new Renter() { PersonID = 1, UnitID = 1, StartDate = new DateTime(1980, 01, 01), EndDate = new DateTime(1990, 02, 28) },
-                new Renter() { PersonID = 2, UnitID = 1, StartDate = new DateTime(1990, 03, 01) },
-                new Renter() { PersonID = 3, UnitID = 2, StartDate = new DateTime(1980, 03, 01), EndDate = new DateTime(2000, 01, 01) },
-                new Renter() { PersonID = 1, UnitID = 3, StartDate = new DateTime(1990, 03, 01) },
-                new Renter() { PersonID = 4, UnitID = 4, StartDate = new DateTime(2000, 01, 01) }
+                new Renter() { PersonID = 1, UnitID = 1, Rent = 100M, StartDate = new DateTime(1980, 01, 01), EndDate = new DateTime(1990, 02, 28) },
+                new Renter() { PersonID = 2, UnitID = 1, Rent = 150M, StartDate = new DateTime(1990, 03, 01) },
+                new Renter() { PersonID = 3, UnitID = 2, Rent = 200M, StartDate = new DateTime(1980, 03, 01), EndDate = new DateTime(2000, 01, 01) },
+                new Renter() { PersonID = 1, UnitID = 3, Rent = 250M, StartDate = new DateTime(1990, 03, 01) },
+                new Renter() { PersonID = 4, UnitID = 4, Rent = 300M, StartDate = new DateTime(2000, 01, 01) }
             };
 
             RealEstateProperties = new List<RealEstateProperty>()

SubSonic/Infrastructure/Builders/DbSqlQueryBuilder/DbSqlQueryBuilderQueryProvider.cs

@@ -53,7 +53,15 @@ public TResult ExecuteMethod<TResult>(MethodCallExpression call)
                 {
                     if (unary.Operand is LambdaExpression lambda)
                     {
-                        where = BuildWhere(dbSelect, lambda);
+                        switch (lambda.Body.NodeType)
+                        {
+                            case ExpressionType.MemberAccess:
+                                dbSelect = (DbSelectExpression)BuildSelect(dbSelect, dbSelect.Columns.Where(x => x.PropertyName.Equals(lambda.GetProperty().Name, StringComparison.Ordinal)));
+                                break;
+                            default:
+                                where = BuildWhere(dbSelect, lambda);
+                                break;
+                        }
                     }
                 }
             }
@@ -83,7 +91,7 @@ public TResult ExecuteMethod<TResult>(MethodCallExpression call)
                     throw Error.InvalidOperation($"Method {call.Method.Name} expects data.");
                 }
             }
-            else if (call.Method.Name.In(nameof(Queryable.Count), nameof(Queryable.LongCount)))
+            else if (call.Method.Name.In(nameof(Queryable.Count), nameof(Queryable.LongCount), nameof(Queryable.Min)))
             {
                 if (BuildSelect(dbSelect, where) is DbSelectExpression select)
                 {
@@ -92,9 +100,20 @@ public TResult ExecuteMethod<TResult>(MethodCallExpression call)
                         throw Error.NotSupported(SubSonicErrorMessages.MethodNotSupported.Format(call.Method.Name));
                     }
 
+                    Expression argument = null;
+
+                    if (select.Columns.Count > 1)
+                    {
+                        argument = select.Columns.First(x => x.Property.IsPrimaryKey).Expression;
+                    }
+                    else
+                    {
+                        argument = select.Columns.Single().Expression;
+                    }
+
                     TResult result = Execute<TResult>(DbExpression.DbSelectAggregate(select, new[]
                     {
-                            DbExpression.DbAggregate(typeof(TResult), aggregateType, select.Columns.First(x => x.Property.IsPrimaryKey).Expression)
+                            DbExpression.DbAggregate(typeof(TResult), aggregateType, argument)
                     }));
 
                     if (select.Take is ConstantExpression take)