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//---------------------------------------------------------------------
// <copyright file="Aggregates.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
using System;
using System.Data.Common;
using System.Collections.Generic;
using System.Data.Metadata.Edm;
using System.Data.Common.CommandTrees.Internal;
using System.Diagnostics;
namespace System.Data.Common.CommandTrees
{
/// <summary>
/// Aggregates are pseudo-expressions. They look and feel like expressions, but
/// are severely restricted in where they can appear - only in the aggregates clause
/// of a group-by expression.
/// </summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1709:IdentifiersShouldBeCasedCorrectly", MessageId = "Db")]
public abstract class DbAggregate
{
private readonly DbExpressionList _args;
private readonly TypeUsage _type;
internal DbAggregate(TypeUsage resultType, DbExpressionList arguments)
{
Debug.Assert(resultType != null, "DbAggregate.ResultType cannot be null");
Debug.Assert(arguments != null, "DbAggregate.Arguments cannot be null");
Debug.Assert(arguments.Count == 1, "DbAggregate requires a single argument");
this._type = resultType;
this._args = arguments;
}
/// <summary>
/// Gets the result type of this aggregate
/// </summary>
public TypeUsage ResultType
{
get { return _type; }
}
/// <summary>
/// Gets the list of expressions that define the arguments to the aggregate.
/// </summary>
public IList<DbExpression> Arguments { get { return _args; } }
}
/// <summary>
/// The aggregate type that corresponds to exposing the collection of elements that comprise a group
/// </summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1709:IdentifiersShouldBeCasedCorrectly", MessageId = "Db")]
public sealed class DbGroupAggregate : DbAggregate
{
internal DbGroupAggregate(TypeUsage resultType, DbExpressionList arguments)
: base(resultType, arguments)
{
}
}
/// <summary>
/// The aggregate type that corresponds to the invocation of an aggregate function.
/// </summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1709:IdentifiersShouldBeCasedCorrectly", MessageId = "Db")]
public sealed class DbFunctionAggregate : DbAggregate
{
private bool _distinct;
EdmFunction _aggregateFunction;
internal DbFunctionAggregate(TypeUsage resultType, DbExpressionList arguments, EdmFunction function, bool isDistinct)
: base(resultType, arguments)
{
Debug.Assert(function != null, "DbFunctionAggregate.Function cannot be null");
_aggregateFunction = function;
_distinct = isDistinct;
}
/// <summary>
/// Gets a value indicating whether the aggregate function is applied in a distinct fashion
/// </summary>
public bool Distinct { get { return _distinct; } }
/// <summary>
/// Gets the method metadata that specifies the aggregate function to invoke.
/// </summary>
public EdmFunction Function { get { return _aggregateFunction; } }
}
}
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