Fix improper oledb parameter regex detection

Depends on Issue 174
https://code.google.com/p/dapper-dot-net/issues/detail?id=174

Dapper NET40/SqlMapper.cs

@@ -2533,7 +2533,7 @@ private static IEnumerable<PropertyInfo> FilterParameters(IEnumerable<PropertyIn
 
 
         // look for ? / @ / : *by itself*
-        static readonly Regex smellsLikeOleDb = new Regex(@"(?<![a-zA-Z0-9_])[?@:](?![a-zA-Z0-9_])", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled),
+        static readonly Regex smellsLikeOleDb = new Regex(@"(?<![a-zA-Z0-9@_])[?@:](?![a-zA-Z0-9@_])", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled),
             literalTokens = new Regex(@"\{=([a-zA-Z0-9_]+)\}", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled);
         
         /// <summary>

DapperTests NET45/Tests.cs

@@ -355,5 +355,20 @@ public void Issue22_ExecuteScalar()
                 k.IsNull();
             }
         }
+
+        public void TestAtEscaping()
+        {
+            using (var connection = Program.GetOpenConnection())
+            {
+                var id = connection.QueryAsync<int>(@"
+                    create table #atescaping(id int not null);
+                    insert into #atescaping (id) values (1)
+                    declare @@Name int
+                    select @@Name = @Id+1
+                    select @@Name
+                    ", new Product { Id = 1 }).Result.Single();
+                id.IsEqualTo(2);
+            }
+        }
     }
 }
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