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namespace System.Web.UI.WebControls.Expressions {
using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using System.Web.Resources;
using System.Web.UI;
[
PersistChildren(false),
ParseChildren(true, "ThenByExpressions")
]
public class OrderByExpression : DataSourceExpression {
private const string OrderByMethod = "OrderBy";
private const string ThenByMethod = "ThenBy";
private const string OrderDescendingByMethod = "OrderByDescending";
private const string ThenDescendingByMethod = "ThenByDescending";
private Collection<ThenBy> _thenByExpressions;
public string DataField {
get {
return (string)ViewState["DataField"] ?? String.Empty;
}
set {
ViewState["DataField"] = value;
}
}
public SortDirection Direction {
get {
object o = ViewState["Direction"];
return o != null ? (SortDirection)o : SortDirection.Ascending;
}
set {
ViewState["Direction"] = value;
}
}
[PersistenceMode(PersistenceMode.InnerDefaultProperty)]
public Collection<ThenBy> ThenByExpressions {
get {
if (_thenByExpressions == null) {
//
_thenByExpressions = new Collection<ThenBy>();
}
return _thenByExpressions;
}
}
public override IQueryable GetQueryable(IQueryable source) {
if (source == null) {
return null;
}
if (String.IsNullOrEmpty(DataField)) {
throw new InvalidOperationException(AtlasWeb.Expressions_DataFieldRequired);
}
ParameterExpression pe = Expression.Parameter(source.ElementType, String.Empty);
source = CreateSortQueryable(source, pe, Direction, DataField, false /* isThenBy */);
foreach (ThenBy thenBy in ThenByExpressions) {
source = CreateSortQueryable(source, pe, thenBy.Direction, thenBy.DataField, true /* isThenBy */);
}
return source;
}
private static IQueryable CreateSortQueryable(IQueryable source, ParameterExpression parameterExpression, SortDirection direction, string dataField, bool isThenBy) {
string methodName = isThenBy ? GetThenBySortMethod(direction) : GetSortMethod(direction);
Expression propertyExpression = ExpressionHelper.CreatePropertyExpression(parameterExpression, dataField);
return source.Call(methodName,
Expression.Lambda(propertyExpression, parameterExpression),
source.ElementType,
propertyExpression.Type);
}
private static string GetSortMethod(SortDirection direction) {
switch (direction) {
case SortDirection.Ascending:
return OrderByMethod;
case SortDirection.Descending:
return OrderDescendingByMethod;
default:
Debug.Fail("shouldn't get here!");
return OrderByMethod;
}
}
private static string GetThenBySortMethod(SortDirection direction) {
switch (direction) {
case SortDirection.Ascending:
return ThenByMethod;
case SortDirection.Descending:
return ThenDescendingByMethod;
default:
Debug.Fail("shouldn't get here!");
return null;
}
}
}
}
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