学步园

namespace ExtensionMethods
{
using System;
using System.Collections.Generic;
using System.Linq;

public static class IEnumerableExtensions
    {
/// <summary>
/// Invokes a transform function on each element of a sequence and returns the minimum Double value  
/// if the sequence is not empty; otherwise returns the specified default value.  
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence of values to determine the minimum value of.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <param name="defaultValue">The default value.</param>
/// <returns>The minimum value in the sequence or default value if sequence is empty.</returns>
      public static double MinOrDefault<TSource>(this IEnumerable<TSource> source, Func<TSource, double> selector, double defaultValue)
      {
if (source.Any<TSource>())
return source.Min<TSource>(selector);  

return defaultValue;
      }

/// <summary>
/// Invokes a transform function on each element of a sequence and returns the maximum Double value  
/// if the sequence is not empty; otherwise returns the specified default value.  
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence of values to determine the maximum value of.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <param name="defaultValue">The default value.</param>
/// <returns>The maximum value in the sequence or default value if sequence is empty.</returns>
      public static double MaxOrDefault<TSource>(this IEnumerable<TSource> source, Func<TSource, double> selector, double defaultValue)
      {
if (source.Any<TSource>())
return source.Max<TSource>(selector);  

return defaultValue;
      }


        public static TResult MinOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector, TResult defaultValue)
        {
            if (source.Any())
            {
                return source.Min(selector);
            }
            return defaultValue;

        }


        public static TResult MaxOrDefault<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector, TResult defaultValue)
        {
            if (source.Any())
            {
                return source.Max(selector);
            }
            return defaultValue;
        }

    }
}