Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.Entity/System/Data/SqlClient/SqlGen/SqlBuilder.cs

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+//---------------------------------------------------------------------
+// <copyright file="SqlBuilder.cs" company="Microsoft">
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//
+// @owner  [....]
+// @backupOwner [....]
+//---------------------------------------------------------------------
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace System.Data.SqlClient.SqlGen
+{
+    /// <summary>
+    /// This class is like StringBuilder.  While traversing the tree for the first time, 
+    /// we do not know all the strings that need to be appended e.g. things that need to be
+    /// renamed, nested select statements etc.  So, we use a builder that can collect
+    /// all kinds of sql fragments.
+    /// </summary>
+    internal class SqlBuilder : ISqlFragment
+    {
+        private List<object> _sqlFragments;
+        private List<object> sqlFragments
+        {
+            get
+            {
+                if (null == _sqlFragments)
+                {
+                    _sqlFragments = new List<object>();
+                }
+                return _sqlFragments;
+            }
+        }
+
+
+        /// <summary>
+        /// Add an object to the list - we do not verify that it is a proper sql fragment
+        /// since this is an internal method.
+        /// </summary>
+        /// <param name="s"></param>
+        public void Append(object s)
+        {
+            Debug.Assert(s != null);
+            sqlFragments.Add(s);
+        }
+
+        /// <summary>
+        /// This is to pretty print the SQL.  The writer <see cref="SqlWriter.Write"/>
+        /// needs to know about new lines so that it can add the right amount of 
+        /// indentation at the beginning of lines.
+        /// </summary>
+        public void AppendLine()
+        {
+            sqlFragments.Add("\r\n");
+        }
+
+        /// <summary>
+        /// Whether the builder is empty.  This is used by the <see cref="SqlGenerator.Visit(DbProjectExpression)"/>
+        /// to determine whether a sql statement can be reused.
+        /// </summary>
+        public virtual bool IsEmpty
+        {
+            get { return ((null == _sqlFragments) || (0 == _sqlFragments.Count)); }
+        }
+
+        #region ISqlFragment Members
+
+        /// <summary>
+        /// We delegate the writing of the fragment to the appropriate type.
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="sqlGenerator"></param>
+        public virtual void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            if (null != _sqlFragments)
+            {
+                foreach (object o in _sqlFragments)
+                {
+                    string str = (o as String);
+                    if (null != str)
+                    {
+                        writer.Write(str);
+                    }
+                    else
+                    {
+                        ISqlFragment sqlFragment = (o as ISqlFragment);
+                        if (null != sqlFragment)
+                        {
+                            sqlFragment.WriteSql(writer, sqlGenerator);
+                        }
+                        else
+                        {
+                            throw new InvalidOperationException();
+                        }
+                    }
+                }
+            }
+        }
+
+        #endregion
+    }
+}