Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web/ModelBinding/ViewStateAttribute.cs

@@ -0,0 +1,32 @@
+
+namespace System.Web.ModelBinding {
+
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false, AllowMultiple = false)]
+    public sealed class ViewStateAttribute : ValueProviderSourceAttribute {
+
+        public string Key {
+            get;
+            private set;
+        }
+
+        public ViewStateAttribute()
+            : this(null) {
+        }
+
+        public ViewStateAttribute(string key) {
+            Key = key;
+        }
+
+        public override IValueProvider GetValueProvider(ModelBindingExecutionContext modelBindingExecutionContext) {
+            if (modelBindingExecutionContext == null) {
+                throw new ArgumentNullException("modelBindingExecutionContext");
+            }
+
+            return new ViewStateValueProvider(modelBindingExecutionContext);
+        }
+
+        public override string GetModelName() {
+            return Key;
+        }
+    }
+}