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