Provide GetSchema override for DbConnectionClosed (#26951)

* Provide GetSchema override for DbConnectionClosed

* Change names

* Code review comment

Author: saurabh500

src/System.Data.SqlClient/src/System/Data/ProviderBase/DbConnectionClosed.cs

@@ -59,6 +59,9 @@ public override void EnlistTransaction(Transaction transaction)
             throw ADP.ClosedConnectionError();
         }
 
+        protected internal override DataTable GetSchema(DbConnectionFactory factory, DbConnectionPoolGroup poolGroup, DbConnection outerConnection, string collectionName, string[] restrictions)
+            => throw ADP.ClosedConnectionError();
+
         protected override DbReferenceCollection CreateReferenceCollection()
         {
             throw ADP.ClosedConnectionError();

src/System.Data.SqlClient/tests/FunctionalTests/SqlConnectionBasicTests.cs

@@ -80,6 +80,15 @@ public void SqlConnectionInvalidParameters()
             Assert.Throws<ArgumentException>(() => new SqlConnection("Integrated Security=truee"));
         }
 
+        [Fact]
+        public void ClosedConnectionSchemaRetrieval()
+        {
+            using (SqlConnection connection = new SqlConnection(string.Empty))
+            {
+                Assert.Throws<InvalidOperationException>(() => connection.GetSchema());
+            }
+        }
+
         [Fact]
         public void ConnectionTimeoutTestWithThread()
         {