How Can I Dynamically Specify the Sort Property in a LINQ OrderBy Clause?

Use dynamic parameters to customize OrderBy expressions in LINQ

LINQ’s OrderBy extension method allows you to sort a collection of objects based on one or more properties. But how do you specify which properties to sort using the values ​​passed in as parameters?

Background:

The following code shows basic usage of OrderBy, where the properties are hardcoded:

<code class="language-csharp">List<student> existingStudends = new List<student>{ new Student {...}, new Student {...}};
List<student> orderbyAddress = existingStudends.OrderBy(c => c.Address).ToList();</code>

Dynamic attribute specification:

In order to dynamically specify the properties to be sorted, you can leverage reflection to build the necessary expression tree. Here is an extension method that implements this functionality:

<code class="language-csharp">public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string orderByProperty, bool desc)
{
    string command = desc ? "OrderByDescending" : "OrderBy";
    var type = typeof(TEntity);
    var property = type.GetProperty(orderByProperty);
    var parameter = Expression.Parameter(type, "p");
    var propertyAccess = Expression.MakeMemberAccess(parameter, property);
    var orderByExpression = Expression.Lambda(propertyAccess, parameter);
    var resultExpression = Expression.Call(typeof(Queryable), command, new Type[] { type, property.PropertyType },
                                   source.Expression, Expression.Quote(orderByExpression));
    return source.Provider.CreateQuery<TEntity>(resultExpression);
}</code>

where orderByProperty is the name of the property you want to sort and desc determines whether to sort in descending order (true) or ascending order (false).

Usage:

Using this extension method you can now dynamically sort by any attribute:

<code class="language-csharp">string param = "City";
List<student> orderbyAddress = existingStudends.OrderBy("City", true).ToList(); // 按城市降序排序
List<student> orderbyName = existingStudends.OrderBy("Name", false).ToList(); // 按名称升序排序</code>

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