48 lines
1.9 KiB
C#
48 lines
1.9 KiB
C#
using System.Linq;
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using System.Linq.Expressions;
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namespace System.Web.UI.WebControls {
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public static class QueryExtensions {
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private const string SORT_DIRECTION_DESC = " DESC";
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public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string sortExpression) where T : class {
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if (source == null) {
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throw new ArgumentNullException("source");
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}
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if (String.IsNullOrWhiteSpace(sortExpression)) {
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return source;
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}
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sortExpression = sortExpression.Trim();
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bool isDescending = false;
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// DataSource control passes the sort parameter with a direction
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// if the direction is descending
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if (sortExpression.EndsWith(SORT_DIRECTION_DESC, StringComparison.OrdinalIgnoreCase)) {
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isDescending = true;
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int descIndex = sortExpression.Length - SORT_DIRECTION_DESC.Length;
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sortExpression = sortExpression.Substring(0, descIndex).Trim();
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}
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if (String.IsNullOrEmpty(sortExpression)) {
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return source;
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}
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ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
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MemberExpression property = Expression.Property(parameter, sortExpression);
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LambdaExpression lambda = Expression.Lambda(property, parameter);
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string methodName = (isDescending) ? "OrderByDescending" : "OrderBy" ;
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Expression methodCallExpression = Expression.Call(typeof(Queryable), methodName,
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new Type[] { source.ElementType, property.Type },
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source.Expression, Expression.Quote(lambda));
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return (IQueryable<T>)source.Provider.CreateQuery(methodCallExpression);
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}
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}
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}
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