c# - UserControl.ParentForm 为空

Question

我正在处理一个表单，该表单根据组合框中选定的索引显示多个用户控件之一。该表格用于添加和编辑包含不同数据字段的不同种类的项目(即服务、库存、非库存等)。用户控件需要访问表单上的一些控件，然后才能保留 Linq-to-SQL 对象。

我遇到的问题是 UserControl.ParentForm 的值总是返回 null。我意识到理想情况下控件不应与表单紧密耦合，但我想在考虑我的重构选项之前了解为什么会发生这种情况。

下面，我在表单中包含了添加用户控件的方法和在控件中尝试获取 ParentForm 的方法。有人可以就为什么 ParentForm 可能为 NULL 给我一些建议吗？

表单代码:

void comboBoxEditType_SelectedIndexChanged(object sender, EventArgs e)
{
    string value = comboBoxEditType.SelectedItem.ToString();

    if (value == "DiscountItem")
    {
        if (itemControl != null)
            this.Controls.Remove(itemControl);

        labelControlDescriptionOfType.Text = "Use to subtract a percentage or fixed amount from a total or subtotal. "
                                           + "Do not use this item type for an early payment discount.";

        DiscountItemControl control = new DiscountItemControl();
        control.Location = new Point(13, 110);
        this.Controls.Add(control);
        itemControl = control;
    }
    else if (value == "InventoryItem")
    {
        if (itemControl != null)
            this.Controls.Remove(itemControl);

        labelControlDescriptionOfType.Text = "Use for goods you purchase, track as inventory, and resell.";

        InventoryItemControl control = new InventoryItemControl();
        control.Location = new Point(13, 110);
        this.Controls.Add(control);
        itemControl = control;
    }
    else if (value == "NonInventoryItem")
    {
        if (itemControl != null)
            this.Controls.Remove(itemControl);

        labelControlDescriptionOfType.Text = "Use for goods you buy but don't track, like office supplies, "
                                           + "or materials for a specific job that you charge back to the customer.";

        NonInventoryPartItemControl control = new NonInventoryPartItemControl();
        control.Location = new Point(13, 110);
        this.Controls.Add(control);
        itemControl = control;
    }
    else if (value == "OtherChargeItem")
    {
        if (itemControl != null)
            this.Controls.Remove(itemControl);

        labelControlDescriptionOfType.Text = "Use for miscellaneous labor, material, or part charges, such as delivery charges, "
                                           + "setup fees, and service charges.";

        OtherChargeItemControl control = new OtherChargeItemControl();
        control.Location = new Point(13, 110);
        this.Controls.Add(control);
        itemControl = control;
    }
    else if (value == "ServiceItem")
    {
        if (itemControl != null)
            this.Controls.Remove(itemControl);

        labelControlDescriptionOfType.Text = "Use for services you charge for or purchase, like specialized labor, consulting hours, or "
                                           + "professional fees.";

        ServiceItemControl control = new ServiceItemControl();
        control.Location = new Point(13, 110);
        this.Controls.Add(control);
        itemControl = control;
    }

    // Move the location of buttons
    int btnX = 12 + itemControl.Width + 10;
    btnSaveAndClose.Location = new Point(btnX, btnSaveAndClose.Location.Y);
    btnSaveAndNew.Location = new Point(btnX, btnSaveAndNew.Location.Y);
    btnCancel.Location = new Point(btnX, btnCancel.Location.Y);

    // Center the Make Inactive CheckBox on side of UserControl
    Point point = new Point();
    point.X = btnCancel.Location.X;
    point.Y = itemControl.Location.Y + itemControl.Size.Height / 2;
    checkEditMakeInactive.Location = point;

    // Resize the window to fit fit the control
    int windowWidth = 140 + itemControl.Width;
    int windowHeight = 150 + itemControl.Height;
    this.Size = new Size(windowWidth,windowHeight);

    // Resize the group containing information on the item type
    int groupWidth = itemControl.Width;
    int groupHeight = groupControlType.Height;
    groupControlType.Size = new Size(groupWidth, groupHeight);
    //this.groupControlType.Size

    // Resize the label
    int labelWidth = itemControl.Width - 27 - comboBoxEditType.Size.Width;
    labelControlDescriptionOfType.Size = new Size(labelWidth, labelControlDescriptionOfType.Height);
}

试图获取 ParentForm 的用户控制代码(总是返回 NULL)

private void CopyItemDataFromForm()
{
    currentDiscountItem.Name = textEditItemName_Number.Text;
    if (checkEditSubItemOf.Checked)
    {
        currentDiscountItem.fkParentItem = ComboBoxHelper.getItemFromComboBox(comboBoxEditParentItem);
    }
    currentDiscountItem.SalesDescription = memoEditDescription.Text;
    currentDiscountItem.SalesPrice = Convert.ToDecimal(textEditAmountOrPercent.Text);
    currentDiscountItem.fkIncomeAccount = ComboBoxHelper.getQBLookUpFromComboBox(comboBoxEditAccount);
    currentDiscountItem.fkTaxCode = ComboBoxHelper.getQBLookUpFromComboBox(comboBoxEditTaxCode);


    AddEditItemForm form = this.ParentForm as AddEditItemForm;
    currentDiscountItem.IsActive = !(form.GetMakeInactiveCheckboxValue());
}

Answer 1

你可以试试用Parent属性，获取对象树中这个FrameworkElement的父对象。

var result = this.Parent;