我一直在寻找解决方案，但不知道我在哪里做错了。但是我是第一次做。

我有班同学

class Students
{

    public Image photo { get; set; }


    public bool AddStudent(Students _student)
    {
        Settings mySettings = new Settings();

        SqlCeConnection conn = new SqlCeConnection(mySettings.StudentsConnectionString);
        SqlCeCommand cmd = new SqlCeCommand();
        cmd.CommandType = System.Data.CommandType.Text;
        cmd.Connection = conn;
        cmd.CommandText = "insert into students (firstname, lastname, dob, allergic, allergydetails, memo, address, photo) " +
                            "Values (" +
                            "'" + @FirstName + "'," +
                            "'" + @LastName + "'," +
                            "'" + @Dob + "'," +
                            "'" + @isAllergic + "'," +
                            "'" + @AllergyDetails + "'," +
                            "'" + @Memo + "'," +
                            "'" + @photo + "'," +
                            "'" + @Address + "')";

        cmd.Parameters.Add("@FirstName", _student.FirstName);
        cmd.Parameters.Add("@LastName", _student.LastName);
        cmd.Parameters.Add("@Dob", _student.Dob);
        cmd.Parameters.Add("@isAllergic", _student.isAllergic);
        cmd.Parameters.Add("@AllergyDetails", _student.AllergyDetails);
        cmd.Parameters.Add("@Memo", _student.Memo);


        cmd.Parameters.Add("@photo", _student.photo);

        cmd.Parameters.Add("@Address", _student.Address);

        try
        {
            conn.Open();
            cmd.ExecuteNonQuery();
            conn.Close();
            return true;
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message.ToString());
            return false;
        }
        finally
        {
            if (conn.State == System.Data.ConnectionState.Open) conn.Close();
            cmd = null;
        }
    }

现在，我像这样通过表单传递属性值。

  private void btnAdd_Click(object sender, EventArgs e)
        {

            Students myStudent = new Students();

            myStudent.FirstName = txtFirstName.Text.Trim();
            myStudent.LastName = txtLastName.Text.Trim();
            myStudent.Dob = dtPicker1.Value;
            myStudent.Memo = txtMemo.Text.Trim();
            myStudent.Address = txtAddress.Text.Trim();

            myStudent.photo = Image.FromFile(openFileDialog1.FileName);

            // Insert New Record
            if (myStudent.AddStudent(myStudent))
                MessageBox.Show("Student Added Successfully");


        }

我收到以下错误

从DbType System.Drawing.Bitmap到已知SqlCeType的映射不存在。

但是我不知道为什么我没有成功。任何建议将不胜感激。