77 lines
2.4 KiB
C#
77 lines
2.4 KiB
C#
//---------------------------------------------------------------------
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// <copyright file="OptionalColumn.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//
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// @owner Microsoft
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//---------------------------------------------------------------------
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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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namespace System.Data.SqlClient.SqlGen
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{
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/// <summary>
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/// Represents a column in a select list that should be printed only if it is later used.
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/// Such columns get added by <see cref="SqlGenerator.AddDefaultColumns"/>.
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/// The SymbolUsageManager associated with the OptionalColumn has the information whether the column
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/// has been used based on its symbol.
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/// </summary>
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internal sealed class OptionalColumn
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{
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#region Private State
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private readonly SymbolUsageManager m_usageManager;
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// The SqlBuilder that contains the column building blocks (e.g: "c.X as X1")
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private readonly SqlBuilder m_builder = new SqlBuilder();
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// The symbol representing the optional column
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private readonly Symbol m_symbol;
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#endregion
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#region Internal Methods
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/// <summary>
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/// Append to the "fragment" representing this column
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/// </summary>
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internal void Append(object s)
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{
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m_builder.Append(s);
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}
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internal void MarkAsUsed()
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{
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this.m_usageManager.MarkAsUsed(this.m_symbol);
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}
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#endregion
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#region Constructor
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internal OptionalColumn(SymbolUsageManager usageManager, Symbol symbol)
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{
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this.m_usageManager = usageManager;
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this.m_symbol = symbol;
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}
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#endregion
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#region Internal members
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/// <summary>
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/// Writes that fragment that represents the optional column
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/// if the usage manager says it is used.
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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 bool WriteSqlIfUsed(SqlWriter writer, SqlGenerator sqlGenerator, string separator)
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{
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if (m_usageManager.IsUsed(m_symbol))
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{
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writer.Write(separator);
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m_builder.WriteSql(writer, sqlGenerator);
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return true;
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}
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return false;
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}
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#endregion
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}
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}
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