C# 如何从基类访问派生类字段

我从类库中的ComboBoxItem创建了一个派生类

class CustomComboBoxItem : System.Windows.Controls.ComboBoxItem
{
    public string SupplierID { get; set; }
}

我将每个自定义ComboxBox项分配到ComboxBox中

while (dbReader.Read())
        {
            CustomComboBoxItem BusinessNameItem = new CustomComboBoxItem();
            BusinessNameItem.Content = dbReader["BusinessName"].ToString();
            BusinessNameItem.SupplierID = dbReader["SupplierID"].ToString();

            ComboBoxControl.Items.Add(BusinessNameItem);
        }

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我现在的问题是如何从其他表单访问SupplierID？

将ComboBoxItem强制转换为CustomComboxItem

ComboBoxItem item = .....
CustomBoxItem castedItem  = item as CustomBoxItem;
if(null != castedItem)
{
    var supplier = castedItem.SupplierID;
}

您也可以在foreach循环中执行此操作

foreach(var item in ComboBoxControl.Items)
{
    CustomBoxItem castedItem  = item as CustomBoxItem;
    if(null != castedItem)
    {
        var supplier = castedItem.SupplierID;
    }
}

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您是否尝试将该项目强制转换为CustomComboBoxItem？