hehe

if (e.RowIndex >= 0)

        {
            var selectedRow = dgvStudent.Rows[e.RowIndex];
            string studentID = selectedRow.Cells[0].Value?.ToString();

            if (!string.IsNullOrEmpty(studentID))
            {
                var student = studentService.FindById(studentID);
                if (student != null)
                {
                    ShowAvatar(student.Avatar);
                }
                else
                {
                    picAvatar.Image = null;
                }
            }