原文地址鏈接：http://www.codeproject.com/Articles/415109/How-to-Create-and-Use-a-User-Control-as-a-DLL
PS：用戶控件，不是自定義控件。DLL文件形式，不是ASCX文件形式。
Introduction（說明）
In this section, you will learn how to build a custom control as a DLL. The basic feature of the DLL is we can use it as a usercontol like a .ascx.
在這一章中，你將會學到如何以DLL文件形式創建一個用戶控件。該DLL文件的基本特性是，我們可以像ascx文件那樣將它用作用戶控件。
How to add a JavaScript file in a DLL（如何添加一個JS文件到DLL中）
First create a new project and select Class Library project.（首先創建一個新項目，選擇類庫類型）
Add a JavaScript file and in the Properties window, set properties as in figure 2.（添加一個JavaScript文件，在其屬性窗口中，如圖2所示設置屬性。）
圖2
Now in the AssemblyInfo.cs file, add the following lines. These are very important lines so add exactly the same name of the js file.
然後在AssemblyInfo.cs文件中添加如下幾行，這些行非常重要，因此確保JS文件名書寫正確。
[assembly: System.Web.UI.WebResource("AddUserControl.JSAutoCmp.js", "text/javascript", PerformSubstitution = true)]Now we write code for creating an autocomplete textbox with a listbox control.
接着寫代碼實現一個自動完成功能，隨着文本框TextBox組件輸入的內容的變換，列表框ListBox的選中值隨之更改。
We will create an autotexbox with a listbox. When we type in the textbox our focus automatically will go to the listbox matched item. We write
[ToolboxData(@"<{0}:AutoCmp_TextBox runat=""server"" \>")]. By
ToolboxData, we specify the tag which is added to the page when this control is dragged form the toolbox to a form. We use
AutoCompleteType which enables us to associate an AutoComplete class with the
TextBox control.
我們要創建的用戶控件是一個文本框控制的自動完成列表框。當我們在文本框中輸入內容時，列表框中批評項會自動獲取焦點。
在類前加入屬性內容：
[ToolboxData(@"<{0}:AutoCmp_TextBox runat=""server"" \>")]PS：該屬性內容用於工具箱操作上。
通過工具箱數據ToolBoxData，我們指定了當該控件被從工具箱拖放到窗體後，頁面文件中要添加的標籤。
PS：類庫項目中，添加文件選擇普通類文件，然後引入和Web相關的命名空間即可。
[ToolboxData(@"<{0}:AutoCmp_TextBox runat=""server"" \>")]
public class AutoComplete_TextBox : TextBox
{
private string _AutoComplete_ListBoxId = "";
private string _Selected_Value = "-1";
public AutoComplete_TextBox()
: base()
{
this.AutoCompleteType = AutoCompleteType.Disabled;
}
[Category("Behavior"), DefaultValue(""),
Description("The AutoComplete_ListBox's Id which will apear on key press.")]
public string AutoComplete_ListBoxId
{
get { return _AutoComplete_ListBoxId; }
set { _AutoComplete_ListBoxId = value.Trim(); }
}
[Category("Behavior"), DefaultValue(""),
Description("Selected value in assossiated AutoComplete_ListBoxId.")]
public string Selected_Value
{
get
{
try
{
if (HttpContext.Current.Request.Form.Count > 0 && _AutoComplete_ListBoxId.Trim() != "")
if (HttpContext.Current.Request.Form["SanControls_HdnField"] != null)
_Selected_Value = get_SelectedValue(HttpContext.Current.Request.Form["SanControls_HdnField"]);
return _Selected_Value;
}
catch { return "-1"; }
}
set { _Selected_Value = value; }
}
private void setCtrl_Attribute(string Attr_name, string value)
{
if (Attr_name != null && Attr_name != "" && value != null && value != "")
{
if (this.Attributes[Attr_name] != null && this.Attributes[Attr_name] != "")
{
if (this.Attributes[Attr_name].IndexOf(value, StringComparison.OrdinalIgnoreCase) == -1)
this.Attributes[Attr_name] = value + ";" + this.Attributes[Attr_name];
}
else
this.Attributes[Attr_name] = value + ";";
}
}
private string get_SelectedValue(string viewState)
{
string retVal = _Selected_Value;
string[] values ={ "|;" };
if (viewState != null)
{
values = viewState.Split(values, StringSplitOptions.None);
for (int i = 0; i < values.Length; i++)
{
if (values[i].Trim() != "" && values[i].Substring(0, values[i].IndexOf("=")) == this.ClientID)
{
retVal = values[i].Substring(values[i].IndexOf("=") + 1).Trim();
break;
}
}
}
return retVal;
}
protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
{
writer.AddAttribute("SelectedIndex", "-1");
writer.AddAttribute("SelectedValue", Selected_Value);
base.AddAttributesToRender(writer);
}
protected override void OnPreRender(EventArgs e)
{
if (AutoComplete_ListBoxId != "")
{
setCtrl_Attribute("onkeyup", "SanControls_selectItem()");
//"return SanControls_showList('" +
// Page.FindControl(AutoCompleteListId).ClientID + "')");
setCtrl_Attribute("onblur", "SanControls_hideList()");
setCtrl_Attribute("onkeydown", "checkKey('" +
Page.FindControl(AutoComplete_ListBoxId).ClientID + "')");
setCtrl_Attribute("onfocus", "SanControls_TextFocus('" +
Page.FindControl(AutoComplete_ListBoxId).ClientID + "')");
}
Page.RegisterRequiresPostBack(this);
Page.ClientScript.RegisterClientScriptInclude("SanControlsJS",
Page.ClientScript.GetWebResourceUrl(this.GetType(), "AddUserControl.JSAutoCmp.js"));
base.OnPreRender(e);
}
}AutoComplete_ListBoxId: By this we assign the listbox ID to the textbox in which we find the matched value and set focus on this item of the listbox. We call the
Page.RegisterRequiresPostBack() method inside (or before) the control's
PreRender() event to tell page that our control is interested in receiving postback data. All the client-side functionalities happen in an external JavaScript file. A JavaScript include is rendered by the control in its
OnPreRender() method. This line is included in the JavaScript file.
AutoComplete_ListBoxId字段說明：通過爲該字段賦值，我們在文本框內容改變時，設置要更改的列表框的項。
Page.ClientScript.RegisterClientScriptInclude("SanControlsJS",
Page.ClientScript.GetWebResourceUrl(this.GetType(), "AddUserControl.JSAutoCmp.js"));
Now we will create a listbox in which we find the value of the textbox.
現在我們要創建一個列表框ListBox，在列表框中有TextBox輸入的內容的匹配項。
[ToolboxData(@"<{0}:AutoCmp_ListBox runat=""server"" \>")]
public class AutoCmp_ListBox : ListBox
{
bool isrendered = false;
public AutoCmp_ListBox()
: base()
{
this.Rows = 7;
}
protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
{
isrendered = true;
writer.AddAttribute("onMouseDown", "SanControls_SelectList();");
writer.AddAttribute("onDblClick", "SanControls_hideList(true);");
writer.AddAttribute("onMouseOut", "SanControls_deSelectList();");
writer.AddAttribute("onMouseUp", "SanControls_deSelectList();");
writer.AddAttribute("onChange", "SanControls_changeText();");
base.AddAttributesToRender(writer);
}
protected override void OnPreRender(EventArgs e)
{
if (!isrendered)
{
if (this.Style.Value != null)
this.Style.Value += "position:absolute;visibility:hidden;width:0px";
else
this.Style.Value = "position:absolute;visibility:hidden;width:0px";
Page.ClientScript.RegisterClientScriptInclude("SanControlsJS",
Page.ClientScript.GetWebResourceUrl(this.GetType(), "AddUserControl.JSAutoCmp.js"));
base.OnPreRender(e);
if (HttpContext.Current.Request.Form["SanControls_HdnField"] == null)
Page.ClientScript.RegisterHiddenField("SanControls_HdnField", "");
else
Page.ClientScript.RegisterHiddenField("SanControls_HdnField",
HttpContext.Current.Request.Form["SanControls_HdnField"]);
}
}
}
We build the DLL then add a New Website and add a reference of this DLL. In our aspx page, we register the assembly just as we use user controls.
編譯該項目爲一DLL文件，然後添加一個新的Website 網站（Web項目），並添加該DLL的引用。
在web項目的aspx文件中，像使用用戶控件ascx一樣添加assembly信息。
aspx page design
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Assembly ="AddUserControl" Namespace="AddUserControl" TagPrefix ="SANCtrl" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<SANCtrl:AutoComplete_TextBox runat ="server" id="sanTextBox" AutoComplete_ListBoxId ="sanListBox" ></SANCtrl:AutoComplete_TextBox>
<SANCtrl:AutoCmp_ListBox runat ="server" ID ="sanListBox" ></SANCtrl:AutoCmp_ListBox>
</div>
</form>
</body>
Now the .cs page code for setting the texbox's listbox ID for searching and filling the list box with data. When we view this page in browser and type in the texbox, the listbox appears and our focus goes on to the matched item of the list box. We do not require any code for this.
sanTextBox.AutoComplete_ListBoxId = sanListBox.UniqueID;
DataTable dt = new DataTable();
dt.Columns.Add("id");
dt.Columns.Add("Name");
dt.Rows.Add("1.", "Aashish Bhatia");
dt.Rows.Add("2.", "Anoop Bhatia");
dt.Rows.Add("3.", "Diljit Singh");
dt.Rows.Add("4.", "Rajeev Sharma");
dt.Rows.Add("5.", "Sanjay Bhatia");
sanListBox.DataTextField = "Name";
sanListBox.DataValueField = "Id";
sanListBox.DataSource = dt;
sanListBox.DataBind();See the figure below which shows the functionality of the autocomplete text box with listbox.
See this figure of the Solution Explorer in which I display the DLL project and a website page for testing if the js functions are assigned to the ASPX controls or not.