Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

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

@@ -0,0 +1,50 @@
+using System.Globalization;
+
+namespace System.Web.ModelBinding {
+    /// <summary>
+    /// This value provider supports single key-value lookup.
+    /// SimpleValueProvider itself is unaware of actual look-up mechanism and delegates to child classes using the FetchValue method.
+    /// Example simple value providers are ViewStateValueProvider and ControlValueProvider.
+    /// </summary>
+    public abstract class SimpleValueProvider : IValueProvider {
+
+        private CultureInfo _cultureInfo;
+
+        protected ModelBindingExecutionContext ModelBindingExecutionContext {
+            get;
+            private set;
+        }
+
+        protected SimpleValueProvider(ModelBindingExecutionContext modelBindingExecutionContext)
+            : this(modelBindingExecutionContext, CultureInfo.CurrentCulture) {
+        }
+
+        protected SimpleValueProvider(ModelBindingExecutionContext modelBindingExecutionContext, CultureInfo cultureInfo) {
+            ModelBindingExecutionContext = modelBindingExecutionContext;
+            _cultureInfo = cultureInfo;
+        }
+
+        public virtual bool ContainsPrefix(string prefix) {
+            if (prefix == null) {
+                throw new ArgumentNullException("prefix");
+            }
+
+            return FetchValue(prefix) != null;
+        }
+
+        public virtual ValueProviderResult GetValue(string key) {
+            if (key == null) {
+                throw new ArgumentNullException("key");
+            }
+
+            object rawValue = FetchValue(key);
+            if (rawValue == null) {
+                return null;
+            }
+            string attemptedValue = Convert.ToString(rawValue, _cultureInfo);
+            return new ValueProviderResult(rawValue, attemptedValue, _cultureInfo);
+        }
+
+        protected abstract object FetchValue(string key);
+    }
+}