Alternative to GetFormatProvider()

Author: ajgorhoe

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

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Text;
+
+namespace IGLib.Alt;
+
+
+public class DefaultFormatProviderSelector
+{
+
+    /// <summary>Returns the global <see cref="IDefaultFormatProviderSelector"/> that is used to provide
+    /// the <see cref="IFormatProvider"/> when one is not specified, and also the the
+    /// <see cref="IDefaultFormatProviderSelector"/> is not specified.</summary>
+    public static IDefaultFormatProviderSelector Global { get; private set; }
+        = new DefaultFormatProviderSelectorInvariantCulture();
+
+    /// <summary>Sets (changes) the global <see cref="IDefaultFormatProviderSelector"/>, which will be
+    /// used by default to select the default <see cref="IFormatProvider"/> object when one is not
+    /// specified, and the <see cref="IDefaultFormatProviderSelector"/> to obtain the default value
+    /// is also not specified.</summary>
+    /// <param name="selector">The <see cref="IDefaultFormatProviderSelector"/> that will be returned
+    /// by the <see cref="DefaultFormatProviderSelector.Global"/> property after this call.
+    /// The marameter may not be null (otherwise, this method throws an exception).</param>
+    /// <exception cref="ArgumentNullException">When the <paramref name="selector"/> parameter is null.</exception>
+    public static void SetGlobal(IDefaultFormatProviderSelector selector) 
+    {
+        if (selector == null)
+        {
+            throw new ArgumentNullException(nameof(selector), "The global selector of default format provider cannot be set to null.");
+        }
+        Global = selector;
+    }
+
+    /// <summary>Returns the appropriate <see cref="IFormatProvider"/> according to the specified (suggested)
+    /// <paramref name="specifiedFormatProvider"/> (that can be null) and the specified <paramref name="defaultSelector"/>,
+    /// which provides the default <see cref="IFormatProvider"/> when the <paramref name="specifiedFormatProvider"/>
+    /// is null If both parameters are null then the default <see cref="IFormatProvider"/> is provided by the
+    /// <see cref="DefaultFormatProviderSelector.Global"/> property.</summary>
+    /// <param name="specifiedFormatProvider">The specified <see cref="IFormatProvider"/>. If not null then this
+    /// object is returned immediately, otherwise the <paramref name="defaultSelector"/> parameter is used to 
+    /// provide the object that is returned.</param>
+    /// <param name="defaultSelector">Provides the default <see cref="IFormatProvider"/> (via the 
+    /// <see cref="IDefaultFormatProviderSelector.DefaultFormatProvider"/> property) in case that the <paramref name="specifiedFormatProvider"/>
+    /// is null. In that case, if this parameter is also null, the <see cref="DefaultFormatProviderSelector.Global"/> provides the
+    /// default object to be returned.</param>
+    /// <returns>The <see cref="IFormatProvider"/> returned according to method parameters:
+    /// <para>* If <paramref name="specifiedFormatProvider"/> is not null, this object is returned.</para>
+    /// <para>* Otherwise, if <paramref name="defaultSelector"/> is not null then the object obtained by its 
+    /// <see cref="IDefaultFormatProviderSelector.DefaultFormatProvider"/> property is returned.</para>
+    /// <para>Otherwise, the format provider obtained by the <see cref="DefaultFormatProviderSelector.Global"/>'s 
+    /// <see cref="IDefaultFormatProviderSelector.DefaultFormatProvider"/> property is returned.</para></returns>
+    /// <remarks>Default parameters are intentionally not provided, such that the caller needs to consciously
+    /// provide null values if this is itended.</remarks>
+    [Obsolete("Replaced with ResolveFormatProvider(IFormatProvider?, IDefaultFormatProviderSelector?)")]
+    public static IFormatProvider GetFormatProvider(IFormatProvider? specifiedFormatProvider,
+        IDefaultFormatProviderSelector? defaultSelector)
+    {
+        return (specifiedFormatProvider ?? (defaultSelector ?? Global).DefaultFormatProvider);
+    }
+
+    public static IFormatProvider ResolveFormatProvider(
+    IFormatProvider? specifiedFormatProvider,
+    IDefaultFormatProviderSelector? defaultSelector)
+    {
+        return specifiedFormatProvider ?? (defaultSelector ?? Global).DefaultFormatProvider;
+    }
+
+
+}