Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System/compmod/system/componentmodel/IDataErrorInfo.cs

@@ -0,0 +1,32 @@
+//------------------------------------------------------------------------------
+// <copyright file="IDataErrorInfo.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.ComponentModel {
+
+    using System;
+
+    /// <devdoc>
+    /// </devdoc>
+    // suppose that you have some data that can be indexed by use of string:
+    // then there are two types of errors:
+    // 1. an error for each piece of data that can be indexed
+    // 2. an error that is valid on the entire data
+    //
+    public interface IDataErrorInfo {
+
+        /// <devdoc>
+        /// </devdoc>
+        string this[string columnName] {
+            get;
+        }
+        /// <devdoc>
+        ///    <para>[To be supplied.]</para>
+        /// </devdoc>
+        string Error {
+            get;
+        }
+    }
+}