private async void btnAdd_Click(object sender, EventArgs e)
        {
            TestDB test = new TestDB();

            if (txtId.Text != "Id")
            {
                test.Id = Int32.Parse(txtId.Text);
            }

            test.Name = txtName.Text;
            //if (txtSubjectId.Text != "SubjectId")
            //{
            //    test.Subject = Int32.Parse(txtSubjectId.Text);
            //}
            //else
            //{
            //    test.Subject = subject.Id;
            //}
            test.Subject = subject.Id;

            test.Quantity     = Int32.Parse(txtQuantity.Text);
            test.QuantityPass = Int32.Parse(txtQuantityPass.Text);
            ApplicationViewModel applicationViewModel = new ApplicationViewModel();
            await applicationViewModel.AddTest(user.Login, user.Password, test);

            testForm.dataGridView.Rows.Clear();
            await applicationViewModel.GetTests(user.Login, user.Password);

            foreach (var t in applicationViewModel.handbookTests)
            {
                var rowNumber = testForm.dataGridView.Rows.Add();
                testForm.dataGridView.Rows[rowNumber].Cells["Id"].Value           = t.Id;
                testForm.dataGridView.Rows[rowNumber].Cells["GradeName"].Value    = t.GradeNumber.ToString() + t.GradeName;
                testForm.dataGridView.Rows[rowNumber].Cells["GradeId"].Value      = t.GradeId;
                testForm.dataGridView.Rows[rowNumber].Cells["GradeNumber"].Value  = t.GradeNumber;
                testForm.dataGridView.Rows[rowNumber].Cells["testName"].Value     = t.Name;
                testForm.dataGridView.Rows[rowNumber].Cells["SubjectId"].Value    = t.SubjectId;
                testForm.dataGridView.Rows[rowNumber].Cells["SubjectName"].Value  = t.SubjectName;
                testForm.dataGridView.Rows[rowNumber].Cells["Quantity"].Value     = t.Quantity;
                testForm.dataGridView.Rows[rowNumber].Cells["QuantityPass"].Value = t.QuantityPass;
            }
            this.Close();
        }