--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Source/Data/Sql/SqlExpression.cs	Thu Mar 27 21:46:09 2014 +0400
@@ -0,0 +1,180 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BLToolkit.Data.Sql
+{
+	public class SqlExpression : ISqlExpression
+	{
+		public SqlExpression(Type systemType, string expr, int precedence, params ISqlExpression[] parameters)
+		{
+			if (parameters == null) throw new ArgumentNullException("parameters");
+
+			foreach (var value in parameters)
+				if (value == null) throw new ArgumentNullException("parameters");
+
+			SystemType = systemType;
+			Expr       = expr;
+			Precedence = precedence;
+			Parameters = parameters;
+		}
+
+		public SqlExpression(string expr, int precedence, params ISqlExpression[] parameters)
+			: this(null, expr, precedence, parameters)
+		{
+		}
+
+		public SqlExpression(Type systemType, string expr, params ISqlExpression[] parameters)
+			: this(systemType, expr, Sql.Precedence.Unknown, parameters)
+		{
+		}
+
+		public SqlExpression(string expr, params ISqlExpression[] parameters)
+			: this(null, expr, Sql.Precedence.Unknown, parameters)
+		{
+		}
+
+		public Type             SystemType { get; private set; }
+		public string           Expr       { get; private set; }
+
+		public int              Precedence { get; private set; }
+		public ISqlExpression[] Parameters { get; private set; }
+
+		#region Overrides
+
+#if OVERRIDETOSTRING
+
+		public override string ToString()
+		{
+			return ((IQueryElement)this).ToString(new StringBuilder(), new Dictionary<IQueryElement,IQueryElement>()).ToString();
+		}
+
+#endif
+
+		#endregion
+
+		#region ISqlExpressionWalkable Members
+
+		[Obsolete]
+		ISqlExpression ISqlExpressionWalkable.Walk(bool skipColumns, Func<ISqlExpression,ISqlExpression> func)
+		{
+			for (var i = 0; i < Parameters.Length; i++)
+				Parameters[i] = Parameters[i].Walk(skipColumns, func);
+
+			return func(this);
+		}
+
+		#endregion
+
+		#region IEquatable<ISqlExpression> Members
+
+		bool IEquatable<ISqlExpression>.Equals(ISqlExpression other)
+		{
+			return Equals(other, DefaultComparer);
+		}
+
+		#endregion
+
+		#region ISqlExpression Members
+
+		public bool CanBeNull()
+		{
+			foreach (var value in Parameters)
+				if (value.CanBeNull())
+					return true;
+
+			return false;
+		}
+
+		public static Func<ISqlExpression,ISqlExpression,bool> DefaultComparer = (x, y) => true;
+
+		public bool Equals(ISqlExpression other, Func<ISqlExpression,ISqlExpression,bool> comparer)
+		{
+			if (this == other)
+				return true;
+
+			var expr = other as SqlExpression;
+
+			if (expr == null || SystemType != expr.SystemType || Expr != expr.Expr || Parameters.Length != expr.Parameters.Length)
+				return false;
+
+			for (var i = 0; i < Parameters.Length; i++)
+				if (!Parameters[i].Equals(expr.Parameters[i], comparer))
+					return false;
+
+			return comparer(this, other);
+		}
+
+		#endregion
+
+		#region ICloneableElement Members
+
+		public ICloneableElement Clone(Dictionary<ICloneableElement, ICloneableElement> objectTree, Predicate<ICloneableElement> doClone)
+		{
+			if (!doClone(this))
+				return this;
+
+			ICloneableElement clone;
+
+			if (!objectTree.TryGetValue(this, out clone))
+			{
+				objectTree.Add(this, clone = new SqlExpression(
+					SystemType,
+					Expr,
+					Precedence,
+					Parameters.Select(e => (ISqlExpression)e.Clone(objectTree, doClone)).ToArray()));
+			}
+
+			return clone;
+		}
+
+		#endregion
+
+		#region IQueryElement Members
+
+		public QueryElementType ElementType { get { return QueryElementType.SqlExpression; } }
+
+		StringBuilder IQueryElement.ToString(StringBuilder sb, Dictionary<IQueryElement,IQueryElement> dic)
+		{
+			var len = sb.Length;
+			var ss  = Parameters.Select(p =>
+			{
+				p.ToString(sb, dic);
+				var s = sb.ToString(len, sb.Length - len);
+				sb.Length = len;
+				return (object)s;
+			});
+			
+			return sb.AppendFormat(Expr, ss.ToArray());
+		}
+
+		#endregion
+
+		#region Public Static Members
+
+		public static bool NeedsEqual(IQueryElement ex)
+		{
+			switch (ex.ElementType)
+			{
+				case QueryElementType.SqlParameter:
+				case QueryElementType.SqlField    :
+				case QueryElementType.Column      : return true;
+				case QueryElementType.SqlFunction :
+
+					var f = (SqlFunction)ex;
+
+					switch (f.Name)
+					{
+						case "EXISTS" : return false;
+					}
+
+					return true;
+			}
+
+			return false;
+		}
+
+		#endregion
+	}
+}