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//---------------------------------------------------------------------
// <copyright file="SqlBuilder.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
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
}
}
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