没有调用C＃按钮事件

Question

很长的代码表示歉意。我的两个按钮taskpagebackbtn和taskpagenextbtn好像没有被调用。我设置了一个消息框，但它没有显示，但是我不确定为什么不调用它们，因为当我打开表单时，当我单击按钮时，它们似乎没有作用。

public partial class Task_Page : Form
{

    TextBox[] subjectnamearray { get; set; }
    List<string> datatablesubjectnamearray { get; set; }
    int numofsubjects { get; set; }


    public Task_Page(TextBox[] subjectnamearray, List<string> datatablesubjectnamearray, int numofsubjects)
    {
        InitializeComponent();
        numoftasks.SelectedIndexChanged += (sender2, e2) => numoftasks_SelectedIndexChanged(sender2, e2,subjectnamearray, datatablesubjectnamearray, numofsubjects);

    }





    private void taskpagebackbtn_Click(object sender, EventArgs e)
    {
        this.Hide();
        var SubjectPage = new SubjectPage();
        SubjectPage.Closed += (s, args) => this.Close();
        SubjectPage.Show();
        SubjectPage.StartPosition = FormStartPosition.Manual;
        SubjectPage.Location = new Point(this.Location.X, this.Location.Y);
    }

    private void taskpagenextbtn_Click(object sender, EventArgs e)
    {
        Marks_and_Weighting_Table marksandweightingtable = new Marks_and_Weighting_Table(subjectnamearray, datatablesubjectnamearray, numofsubjects);


        foreach (Control control in this.Controls)
        {
            if (control is TextBox)
            {
                if (control.Text.Trim() == string.Empty)
                {
                    MessageBox.Show("Please fill out all textboxes.", "Error Message");
                    /*https://www.codeproject.com/Questions/496674/EmptyplusTextboxplusValidationplusinplusC*/

                    return;
                }
            }
        }
        this.Hide();    
        var MarksandWeightingTable = new Marks_and_Weighting_Table(subjectnamearray, datatablesubjectnamearray, numofsubjects);
        MarksandWeightingTable.Closed += (s, args) => this.Close();
        MarksandWeightingTable.Show();
        MarksandWeightingTable.StartPosition = FormStartPosition.Manual;
        MarksandWeightingTable.Location = new Point(this.Location.X, this.Location.Y);
    }

    private void numoftasks_SelectedIndexChanged(object sender, EventArgs e, TextBox[] subjectnamearray, List<string> datatablesubjectnamearray, int numofsubjects)
    {
        lblsubjectname1.Text = subjectnamearray[0].Text;
        lblsubjectname2.Text = subjectnamearray[1].Text;
        lblsubjectname3.Text = subjectnamearray[2].Text;
        lblsubjectname4.Text = subjectnamearray[3].Text;
        lblsubjectname5.Text = subjectnamearray[4].Text;
        lblsubjectname6.Text = subjectnamearray[5].Text;
        /*https://stackoverflow.com/questions/2916684/c-sharp-net-change-label-text*/