Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web.DynamicData/DynamicData/Util/AttributeExtensions.cs

@@ -0,0 +1,67 @@
+namespace System.Web.DynamicData.Util {
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;    
+
+    internal static class AttributeExtensions {
+        /// <summary>
+        /// Gets the first attribute of a given time on the target AttributeCollection, or null.
+        /// </summary>
+        /// <typeparam name="TAttribute">The attribute type</typeparam>
+        /// <param name="attributes">The AttributeCollection object</param>
+        /// <returns></returns>
+        internal static TAttribute FirstOrDefault<TAttribute>(this System.ComponentModel.AttributeCollection attributes) where TAttribute : Attribute {
+            return attributes.OfType<TAttribute>().FirstOrDefault();
+        }
+
+        internal static TResult GetAttributePropertyValue<TAttribute, TResult>(this System.ComponentModel.AttributeCollection attributes, Func<TAttribute, TResult> propertyGetter)
+            where TResult : class
+            where TAttribute : Attribute {
+
+            return attributes.GetAttributePropertyValue(propertyGetter, null);
+        }
+
+        internal static TResult GetAttributePropertyValue<TAttribute, TResult>(this System.ComponentModel.AttributeCollection attributes, Func<TAttribute, TResult> propertyGetter, TResult defaultValue)
+            where TAttribute : Attribute {
+
+            var attribute = attributes.FirstOrDefault<TAttribute>();
+
+            return attribute.GetPropertyValue<TAttribute, TResult>(propertyGetter, defaultValue);
+        }
+
+        /// <summary>
+        /// Gets the property for a given attribute reference or returns null if the reference is null.
+        /// </summary>
+        /// <typeparam name="TAttribute">The attribute type</typeparam>
+        /// <typeparam name="TResult">The type of the attribute's property</typeparam>
+        /// <param name="attribute">The attribute reference</param>
+        /// <param name="propertyGetter">The function to evaluate on the attribute</param>
+        /// <returns></returns>
+        internal static TResult GetPropertyValue<TAttribute, TResult>(this TAttribute attribute, Func<TAttribute, TResult> propertyGetter)
+            where TResult : class
+            where TAttribute : Attribute {
+
+            return attribute.GetPropertyValue(propertyGetter, null);
+        }
+
+        /// <summary>
+        /// Gets the property for a given attribute reference or returns the default value if the reference is null.
+        /// </summary>
+        /// <typeparam name="TAttribute">The attribute type</typeparam>
+        /// <typeparam name="TResult">The type of the attribute's property</typeparam>
+        /// <param name="attribute">The attribute reference</param>
+        /// <param name="propertyGetter">The function to evaluate on the attribute</param>
+        /// <param name="defaultValue">The default value to return if the attribute is null</param>
+        /// <returns></returns>
+        internal static TResult GetPropertyValue<TAttribute, TResult>(this TAttribute attribute, Func<TAttribute, TResult> propertyGetter, TResult defaultValue)
+            where TAttribute : Attribute {
+
+            if (attribute != null) {
+                return propertyGetter(attribute);
+            }
+            else {
+                return defaultValue;
+            }
+        }
+    }
+}