annotations/Azaion.Common/Extensions/QueryableExtensions.cs

using System.Linq.Expressions;

namespace Azaion.Common.Extensions;

public static class QueryableExtensions
{
    /// <summary>
    /// Adds Where true predicate only if result of condition is true.
    /// If false predicate provided, uses it in case of false result
    /// Useful for filters, when filters should be applied only when it was set (not NULL)
    /// </summary>
    public static IQueryable<TSource> WhereIf<TSource>(this IQueryable<TSource> query, bool? condition,
        Expression<Func<TSource, bool>> truePredicate,
        Expression<Func<TSource, bool>>? falsePredicate = null)
    {
        if (!condition.HasValue)
            return query;

        if (condition.Value)
            return query.Where(truePredicate);

        return falsePredicate != null
            ? query.Where(falsePredicate)
            : query;
    }

    /// <summary>
    /// Adds Where true predicate only if result of condition is true.
    /// If false predicate provided, uses it in case of false result
    /// Useful for filters, when filters should be applied only when it was set (not NULL)
    /// </summary>
    public static IEnumerable<TSource> WhereIf<TSource>(this IEnumerable<TSource> query, bool? condition,
        Func<TSource, bool> truePredicate,
        Func<TSource, bool>? falsePredicate = null)
    {
        if (!condition.HasValue)
            return query;

        if (condition.Value)
            return query.Where(truePredicate);

        return falsePredicate != null
            ? query.Where(falsePredicate)
            : query;
    }

}