Include property via reflection

Question

I am trying to .Include() properties of a model via reflection, allowing me to automatically include all properties of any model type.

public static IQueryable<TSource> IncludeAll
    <TSource>(this IQueryable<TSource> source)
    where TSource : class
{
    return typeof(TSource).GetProperties()
        .Where(property => property.GetGetMethod().IsVirtual)
        .Aggregate(
            source,
            (current, property) => current.Include(
                item => property.GetValue(item, null)));
}

The error I get is

InvalidOperationException: The property expression 'item => __property_0.GetValue(item, null)' is not valid. The expression should represent a property access: 't => t.MyProperty'.

Is there any way to actually reference the property by its accessor in the lambda?

Tseng Tseng · Accepted Answer · 2017-08-17T14:34:53

Exception says it.

The .Include() uses expression trees, not delegates or arbitrary values (you are only returning the value of the property, not the property itself) .

public static IIncludableQueryable<TEntity, TProperty> Include<TEntity, TProperty>([NotNullAttribute] this IQueryable<TEntity> source, [NotNullAttribute] Expression<Func<TEntity, TProperty>> navigationPropertyPath) where TEntity : class;

But building an expression tree is complicated.

Instead it's easier to use the string override of .Include(), i.e. .Include("MyProperty.ChildProperty.GrandchildProperty"). And building the string is easy enough via reflection.

Include property via reflection

1 Answers