Added support Concat string in SqlExpression

Author: OlegNadymov

src/ServiceStack.OrmLite.Firebird/FirebirdSqlExpression.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.Linq.Expressions;
 
 namespace ServiceStack.OrmLite.Firebird
@@ -29,6 +30,11 @@ protected override object VisitColumnAccessMethod(MethodCallExpression m)
             }
             return new PartialSqlString(statement);
         }
+
+        protected override PartialSqlString ToConcatPartialString(List<object> args)
+        {
+            return new PartialSqlString(string.Join(" || ", args));
+        }
     }
 }
 

src/ServiceStack.OrmLite.MySql/MySqlExpression.cs

@@ -1,8 +1,15 @@
-namespace ServiceStack.OrmLite.MySql
+using System.Collections.Generic;
+
+namespace ServiceStack.OrmLite.MySql
 {
     public class MySqlExpression<T> : SqlExpression<T>
     {
         public MySqlExpression(IOrmLiteDialectProvider dialectProvider)
             : base(dialectProvider) {}
+
+        protected override PartialSqlString ToConcatPartialString(List<object> args)
+        {
+            return new PartialSqlString(string.Format("CONCAT({0})", string.Join(", ", args)));
+        }
     }
 }

src/ServiceStack.OrmLite.Oracle/OracleSqlExpression.cs

@@ -52,6 +52,11 @@ public override SqlExpression<T> OrderByRandom()
         {
             return base.OrderBy("dbms_random.value");
         }
+
+        protected override PartialSqlString ToConcatPartialString(List<object> args)
+        {
+            return new PartialSqlString(string.Join(" || ", args));
+        }
     }
 }
 

src/ServiceStack.OrmLite.PostgreSQL/PostgreSqlExpression.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.Linq;
 
 namespace ServiceStack.OrmLite.PostgreSQL
@@ -24,6 +25,11 @@ public override SqlExpression<T> OrderByRandom()
         {
             return base.OrderBy("RANDOM()");
         }
+
+        protected override PartialSqlString ToConcatPartialString(List<object> args)
+        {
+            return new PartialSqlString(string.Join(" || ", args));
+        }
     }
 
 }

src/ServiceStack.OrmLite.Sqlite/SqliteExpression.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq.Expressions;
 
 namespace ServiceStack.OrmLite.Sqlite
@@ -76,5 +77,10 @@ public override SqlExpression<T> OrderByRandom()
         {
             return base.OrderBy("random()");
         }
+
+        protected override PartialSqlString ToConcatPartialString(List<Object> args)
+        {
+            ;return new PartialSqlString(String.Join(" || ", args));
+        }
     }
 }

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -1339,6 +1339,9 @@ protected virtual object VisitBinary(BinaryExpression b)
             else if (operand == "<>" && right.ToString().Equals("null", StringComparison.OrdinalIgnoreCase))
                 operand = "is not";
 
+            if (operand == "+" && b.Left.Type == typeof(string) && b.Right.Type == typeof(string))
+                return BuildConcatExpression(new List<object>() {left, right});
+
             VisitFilter(operand, originalLeft, originalRight, ref left, ref right);
 
             switch (operand)
@@ -1708,6 +1711,9 @@ protected virtual object VisitMethodCall(MethodCallExpression m)
             if (IsColumnAccess(m))
                 return VisitColumnAccessMethod(m);
 
+            if (IsStaticStringMethod(m))
+                return VisitStaticStringMethodCall(m);
+
             return CachedExpressionCompiler.Evaluate(m);
         }
 
@@ -1963,6 +1969,44 @@ private object ToInPartialString(Expression memberExpr, object quotedColName)
             return new PartialSqlString(statement);
         }
 
+        private bool IsStaticStringMethod(MethodCallExpression m)
+        {
+            if (m.Object == null && m.Method.Name == "Concat")
+            {
+                return true;
+            }
+
+            return false;
+        }
+
+        protected virtual object VisitStaticStringMethodCall(MethodCallExpression m)
+        {
+            switch (m.Method.Name)
+            {
+                case "Concat":
+                    var args = VisitExpressionList(m.Arguments);
+                    return BuildConcatExpression(args);
+
+                default:
+                    throw new NotSupportedException();
+            }
+        }
+
+        private PartialSqlString BuildConcatExpression(List<object> args)
+        {
+            for (int i = 0; i < args.Count; i++)
+            {
+                if (args[i] as PartialSqlString == null)
+                    args[i] = ConvertToParam(args[i]);
+            }
+            return ToConcatPartialString(args);
+        }
+
+        protected virtual PartialSqlString ToConcatPartialString(List<object> args)
+        {
+            return new PartialSqlString(String.Join(" + ", args));
+        }
+
         protected virtual object VisitSqlMethodCall(MethodCallExpression m)
         {
             List<object> args = this.VisitInSqlExpressionList(m.Arguments);

tests/ServiceStack.OrmLite.Tests/ExpressionVisitorTests.cs

@@ -458,6 +458,28 @@ public void Can_Where_using_filter_with_ToString()
             Assert.That(target.Count, Is.EqualTo(3));
         }
 
+        [Test]
+        public void Can_Where_using_filter_with_Concat()
+        {
+            string filterText = "asdf";
+            int filterInt = 10;
+
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => String.Concat(x.TextCol, x.NullableIntCol.ToString()) == filterText + filterInt;
+            var q = Db.From<TestType>().Where(filter);
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+
+            filter = x => String.Concat(x.TextCol, ".", x.NullableIntCol.ToString()) == filterText + "." + filterInt;
+            q = Db.From<TestType>().Where(filter);
+            target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+
+            filter = x => x.TextCol + "." + x.NullableIntCol.ToString() == filterText + "." + filterInt;
+            q = Db.From<TestType>().Where(filter);
+            target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+        }
+
         private int MethodReturningInt(int val)
         {
             return val;