Enumerable where extension

Author: Jakab László

src/AutSoft.Linq/Enumerable/WhereExtensions.cs

@@ -0,0 +1,53 @@
+namespace AutSoft.Linq.Enumerable;
+
+/// <summary>
+/// Extensions methods for <see cref="IEnumerable{T}"/> with helper functionality for Where methods
+/// </summary>
+public static class WhereExtensions
+{
+    /// <summary>
+    /// Conditionally append a where expression to <see cref="IEnumerable{T}"/> for performance considerations.
+    /// </summary>
+    /// <typeparam name="TSource">Element's type</typeparam>
+    /// <param name="source">An <see cref="IEnumerable{T}" /> to conditionally filter</param>
+    /// <param name="condition">Condition to determine which function to use in Where clause</param>
+    /// <param name="conditionTruePredicate">Function to use if the <paramref name="condition"/> is true</param>
+    /// <param name="conditionFalsePredicate">Optional function to use if the <paramref name="condition"/> is false</param>
+    /// <returns><see cref="IEnumerable{T}"/> with filtering expressions.</returns>
+    public static IEnumerable<TSource> Where<TSource>(
+        this IEnumerable<TSource> source,
+        bool condition,
+        Func<TSource, bool> conditionTruePredicate,
+        Func<TSource, bool>? conditionFalsePredicate = null)
+    {
+        if (condition)
+        {
+            return source.Where(conditionTruePredicate);
+        }
+        else if (conditionFalsePredicate != null)
+        {
+            return source.Where(conditionFalsePredicate);
+        }
+        else
+        {
+            return source;
+        }
+    }
+
+    /// <summary>
+    /// Conditionally append statements to a <see cref="IEnumerable{T}"/> fluent call chain
+    /// in order to keep the fluent syntax
+    /// </summary>
+    /// <typeparam name="TSource">Element's type</typeparam>
+    /// <param name="source">An <see cref="IEnumerable{T}" /> to extend</param>
+    /// <param name="condition">Condition to determine transform the source or not</param>
+    /// <param name="transform">Function which describes the modifications on the <paramref name="source"/>.</param>
+    /// <returns>An extended <see cref="IEnumerable{T}"/></returns>
+    public static IEnumerable<TSource> If<TSource>(
+        this IEnumerable<TSource> source,
+        bool condition,
+        Func<IEnumerable<TSource>, IEnumerable<TSource>> transform)
+    {
+        return condition ? transform(source) : source;
+    }
+}

src/AutSoft.Linq/Queryable/WhereExtensions.cs

@@ -42,7 +42,7 @@ public static IQueryable<TSource> Where<TSource>(
     /// </summary>
     /// <typeparam name="TSource">Element's type</typeparam>
     /// <param name="source">An <see cref="IQueryable{T}" /> to extend</param>
-    /// <param name="condition">Condition to determine which expression to use in Where clause</param>
+    /// <param name="condition">Condition to determine transform the source or not</param>
     /// <param name="transform">Function which describes the modifications on the <paramref name="source"/>.</param>
     /// <returns>An extended <see cref="IQueryable{T}"/></returns>
     public static IQueryable<TSource> If<TSource>(