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POc# - why this OrderBy parameter is wrong?
 

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  1. POc# - why this OrderBy parameter is wrong?
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    <p>I'm running problem with the Delegate and OrderBy extension method. Could anyone please tell me why? Thanks in advance. Below is the whole code:</p> <pre><code>namespace StudyDemo { public class MyDelegate { public delegate TResult DelegateOrder&lt;in T, out TResult&gt;(T arg); } public class Product { public string Name { get; private set; } public decimal? Price { get; set; } public Product(string name, decimal price) { Name = name; Price = price; } /* private parameterless constructor for the sake of the new property-based initialization. */ Product() { } public static List&lt;Product&gt; GetSampleProducts() { return new List&lt;Product&gt; { new Product { Name="West Side Story", Price=9.99m }, new Product { Name="Assassins", Price=14.99m }, new Product { Name="Frogs", Price=13.99m }, new Product { Name="Sweeney Todd", Price=10.99m } }; } public override string ToString() { return string.Format("{0}: {1}", Name, Price); } } public partial class FrmMain : Form { public FrmMain() { InitializeComponent(); } public string myOrder(Product p) { return p.Name; } private void button2_Click(object sender, EventArgs e) { List&lt;Product&gt; products = Product.GetSampleProducts(); Func&lt;Product, string&gt; orderDelegate2 = myOrder; foreach (Product product in products.OrderBy(orderDelegate2)) { /* Do something */ } MyDelegate.DelegateOrder&lt;Product, string&gt; myOrder2 = myOrder; foreach (Product product in products.OrderBy(myOrder2)) /* not functioning, why? */ { /* Do something */ } } } } </code></pre> <p>Note Below: <strong>DelegateOrder</strong> delegate and Func delegate are the same. I just copy the <strong>Func</strong> delegate to <strong>DelegateOrder</strong> delegate.</p> <p>In the above code example, the line <code>foreach (Product product in products.OrderBy(myOrder2))</code> does not functioning, could anyone kindly tell me why?</p> <p>This is the error when you compile the code:</p> <p><code>The type arguments for method 'System.Linq.Enumerable.OrderBy&lt;TSource,TKey&gt;(System.Collections.Generic.IEnumerable&lt;TSource&gt;, System.Func&lt;TSource,TKey&gt;)' cannot be inferred from the usage. Try specifying the type arguments explicitly.</code></p>
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