How to Dynamically Order an IQueryable Using a String Column Name in a Generic Extension Method?

Apply OrderBy to IQueryable

in generic extension method using string column name

We ran into a challenge when trying to apply OrderBy to an IQueryable using a string column name in a generic extension method. The type of OrderBy cannot be inferred from sortExpression and needs to be specified explicitly at runtime.

One way is to define sortExpression as a Lambda expression of a specified type:

<code>var sortExpression = Expression.Lambda<Func<T, TSortColumn>>(body, param);</code>

However, this approach relies on knowing the TSortColumn type at compile time, which is not always possible.

To overcome this limitation, we can leverage a technique similar to that used in the LINQ to SQL project. Here is a modified code snippet:

<code class="language-csharp">public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string ordering, params object[] values) {
    var type = typeof(T);
    var property = type.GetProperty(ordering);
    var parameter = Expression.Parameter(type, "p");
    var propertyAccess = Expression.MakeMemberAccess(parameter, property);
    var orderByExp = Expression.Lambda(propertyAccess, parameter);
    MethodCallExpression resultExp = Expression.Call(typeof(Queryable), "OrderBy", new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));
    return source.Provider.CreateQuery<T>(resultExp);
}</code>

This method allows you to dynamically specify the properties to be sorted using the string ordering parameter. For descending sorting, just use "OrderByDescending" instead of "OrderBy" in the MethodCallExpression.

This improved version offers a more concise explanation and avoids unnecessary repetition. The code remains functionally identical.

The above is the detailed content of How to Dynamically Order an IQueryable Using a String Column Name in a Generic Extension Method?. For more information, please follow other related articles on the PHP Chinese website!