Initial state

samples/angular/MusicStore/Infrastructure/SortExpression.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Threading.Tasks;
+using Microsoft.AspNet.Mvc.ViewFeatures;
+
+namespace MusicStore.Infrastructure
+{
+    public static class SortExpression
+    {
+        private const string SORT_DIRECTION_DESC = " DESC";
+
+        public static IQueryable<TModel> SortBy<TModel, TProperty>(this IQueryable<TModel> query, string sortExpression, Expression<Func<TModel, TProperty>> defaultSortExpression, SortDirection defaultSortDirection = SortDirection.Ascending) where TModel : class
+        {
+            return SortBy(query, sortExpression ?? Create(defaultSortExpression, defaultSortDirection));
+        }
+
+        public static string Create<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression, SortDirection sortDirection = SortDirection.Ascending) where TModel : class
+        {
+            var expressionText = ExpressionHelper.GetExpressionText(expression);
+            // TODO: Validate the expression depth, etc.
+
+            var sortExpression = expressionText;
+
+            if (sortDirection == SortDirection.Descending)
+            {
+                sortExpression += SORT_DIRECTION_DESC;
+            }
+
+            return sortExpression;
+        }
+
+        public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string sortExpression) where T : class
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException("source");
+            }
+
+            if (String.IsNullOrWhiteSpace(sortExpression))
+            {
+                return source;
+            }
+
+            sortExpression = sortExpression.Trim();
+            var isDescending = false;
+
+            // DataSource control passes the sort parameter with a direction
+            // if the direction is descending
+            if (sortExpression.EndsWith(SORT_DIRECTION_DESC, StringComparison.OrdinalIgnoreCase))
+            {
+                isDescending = true;
+                var descIndex = sortExpression.Length - SORT_DIRECTION_DESC.Length;
+                sortExpression = sortExpression.Substring(0, descIndex).Trim();
+            }
+
+            if (string.IsNullOrEmpty(sortExpression))
+            {
+                return source;
+            }
+
+            ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
+
+            // Build up the property expression, e.g.: (m => m.Foo.Bar)
+            var sortExpressionParts = sortExpression.Split('.');
+            Expression propertyExpression = parameter;
+            foreach (var property in sortExpressionParts)
+            {
+                propertyExpression = Expression.Property(propertyExpression, property);
+            }
+
+            LambdaExpression lambda = Expression.Lambda(propertyExpression, parameter);
+
+            var methodName = (isDescending) ? "OrderByDescending" : "OrderBy";
+
+            Expression methodCallExpression = Expression.Call(
+                typeof(Queryable),
+                methodName,
+                new[] { source.ElementType, propertyExpression.Type },
+                source.Expression,
+                Expression.Quote(lambda));
+
+            return (IQueryable<T>)source.Provider.CreateQuery(methodCallExpression);
+        }
+    }
+}