How Can I Extend IQueryable's OrderBy with Generic Column Names?

Extend IQueryable's OrderBy method with generic column names

This article explores how to enhance IQueryable with a generic extension method so that it can be sorted based on a given string column name.

Consider the following extension methods:

<code class="language-csharp">public static IQueryable<TResult> ApplySortFilter<T, TResult>(this IQueryable<T> query, string columnName)
    where T : EntityObject</code>

In order to implement the sorting function, we need to create an expression using the given column name. However, we ran into a problem: the ordering type inferred from the expression did not match the type required by the OrderBy method.

This presents a challenge since the sort type TSortColumn can only be determined at runtime. However, there is a solution.

The provided code example demonstrates a similar approach:

<code class="language-csharp">public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string ordering, params object[] values)</code>

This method accepts a string parameter ordering, which represents the column name. It dynamically generates an expression based on the specified column name and Lambda expression. The resulting expression is then used to create a MethodCallExpression that calls the OrderBy method.

Finally, source.Provider.CreateQuery<T> is called to return the sorted IQueryable.

Modification: For descending sorting:

<code class="language-csharp">MethodCallExpression resultExp = Expression.Call(typeof(Queryable), "OrderByDescending", new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));</code>

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