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以编程方式创建ASP.NET用户控件实例时出现问题

asp.net-3.5 c#

Ben Hoffman · 技术社区 · 14 年前

FileListReader fReader = (FileListReader)LoadControl("~/Controls/FileListReader.ascx");
phFileLists.Controls.Add(fReader);

但是,我想更改控件,以便可以为其提供如下构造函数:

public FileListReader(Int32 itemGroupId, Int32 documentType, String HeaderString, String FooterString, bool isAdminUser)
{
    base.Construct();
    this.itemGroupId = itemGroupId;
    this.documentType = documentType;
    this.HeaderString = HeaderString;
    this.FooterString = FooterString;
    this.isAdminUser = isAdminUser;
}

然后我可以这样调用控件:

FileListReader fReader = (FileListReader)LoadControl(typeof(FileListReader), new Object[] { itemGroupId, 6, "Sell Sheets", "<br /><br />", isAdminUser });

然而,当我这样做时,我总是得到一个错误,我的FileListReader控件中的页内控件没有被实例化,我得到一个空引用错误。例如我有一个 <asp:Label></asp:label> 控制当我尝试在页面上设置文本时出错。是什么原因造成的?我猜 base.Construct()

2 回复 | 直到 14 年前

Tim Hoolihan 14 年前

继承构造函数的正确方法如下:

class FileListReader : WebControl
{
public FileListReader(Int32 itemGroupId, 
                          Int32 documentType, 
                          String HeaderString, 
                          String FooterString, 
                          bool isAdminUser) : base()  // <-- notice the inherit
{

    this.itemGroupId = itemGroupId;
    this.documentType = documentType;
    this.HeaderString = HeaderString;
    this.FooterString = FooterString;
    this.isAdminUser = isAdminUser;
}
  // ... other code here ... //
}

Coding Flow 14 年前

base.Contruct() 是您应该做的,请尝试调用下面基类示例的默认构造函数:

public FileListReader(Int32 itemGroupId, Int32 documentType, String HeaderString, String FooterString, bool isAdminUser) :base()
{
    base.Construct();
    this.itemGroupId = itemGroupId;
    this.documentType = documentType;
    this.HeaderString = HeaderString;
    this.FooterString = FooterString;
    this.isAdminUser = isAdminUser;
}