Added IDefaultFormatProvider interface

Author: ajgorhoe

src/IGLib.Core/Console/Validation/DefaultFormatProvider/IDefaultFormatProvider.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Text;
+
+namespace IGLib
+{
+
+    /// <summary>Provides the default format provider (object of type <see cref="IFormatProvider"/>) 
+    /// for cases where the format provider is not explicitly specified; e.g., in methods where
+    /// <see cref="IFormatProvider"/> is a parameter, but is not provided by the caller (parameter
+    /// is set to null).</summary>
+    /// <remarks><para>Usage example:</para>
+    /// <remarks>In constructors or methods that have <see cref="IFormatProvider"/> as parameter, also 
+    /// provide <see cref="IDefaultFormatProviderSelector?"/> as parameter, and default it to null.
+    /// Then, within the constructor, check if fhe format provider parameter is null, and if yes,
+    /// set it to what the default format provider selector's 
+    /// <see cref="DefaulltFormatProvider"/> returns. In applications, you can arrange for specific 
+    /// <see cref="IDefaultFormatProviderSelector"/> to be injected in all such constructors.</remarks>
+    /// </remarks>
+    public interface IDefaultFormatProviderSelector
+    {
+
+        IFormatProvider DefaulltFormatProvider { get; }
+
+    }
+
+
+}