public string Delete(string server, string instance,  string snapshot)
        {
            DbSnapshotMgr mgr = new DbSnapshotMgr();
            DbConnectionInfo connectionInfo = new DbConnectionInfo(server,instance);
            try
            {
                  mgr.DeleteSnapshot(connectionInfo,snapshot);
            }
            catch (Exception ex)
            {

                return ex.ToString();
            }

            return "Ok";
        }
            public void DeleteSnapshotValid()
            {
                var target = new DbSnapshotMgr();
                var connectionInfo = new DbConnectionInfo(@".\", "SQL2012");
                string snapshotDatabaseName = "Certit_pretest";

                target.DeleteSnapshot(connectionInfo, snapshotDatabaseName);
            }
            public void DeleteSnapshotNoValidDbNameParameters()
            {
                var target = new DbSnapshotMgr();
                var connectionInfo = new DbConnectionInfo();
                string snapshotDatabaseName = string.Empty;

                try
                {
                    target.DeleteSnapshot(connectionInfo, snapshotDatabaseName);
                    Assert.Fail();
                }
                catch (ArgumentNullException ex)
                {
                    Assert.IsTrue(ex.Message.Contains("databaseName"));
                }
            }
            public void DeleteSnapshotMissingDb()
            {
                var target = new DbSnapshotMgr();
                var connectionInfo = new DbConnectionInfo(@".\", "SQL2012");
                string snapshotDatabaseName = "UnknowDatabase";

                try
                {
                    target.DeleteSnapshot(connectionInfo, snapshotDatabaseName);
                }
                catch (ArgumentOutOfRangeException ex)
                {
                    Assert.IsTrue(ex.Message.Contains(snapshotDatabaseName));
                }
            }
            public void DeleteSnapshotDbIsNotASnapshot()
            {
                var target = new DbSnapshotMgr();
                var connectionInfo = new DbConnectionInfo(@".\", "SQL2012");
                string snapshotDatabaseName = "Certit";

                try
                {
                    target.DeleteSnapshot(connectionInfo, snapshotDatabaseName);
                }
                catch (ArgumentException ex)
                {
                    Assert.IsTrue(ex.Message.Contains("is not a snapshot database"));
                }
            }