简单的自定义Combobox控件

 

 

根据前面对复合控件的开发的简单研究,综合前面所学的知识,实现了一个简单的ComboBox的控件的练习,程序的设计思路如下，利用一个input标签、一个Img标签、和前台的window.createPopup()对象生成一个简单的ComboBox控件，将描述此控件的样式文件，和执行的前台的js文件放如一个固定的文件夹my controls中以便用户使用。本示例仅仅实现了简单的combox控件的功能，还有很多地方值得进一步修改。

.具体的实现过程如下.
第一步:建立自定义控件的工程命名为myComboBoxs,至于具体的创建过程在前面已经叙述过了在此不在叙述。
第二步:建立测试工程TestCombobox
第三步:建立描述控件样式的样式表文件和执行前台功能的js文件.

ComboBox具体实现代码如下： 

using  System;
using  System.Collections.Generic;
using  System.ComponentModel;
using  System.Text;
using  System.Web;
using  System.Web.UI;
using  System.Web.UI.WebControls;

[assembly: TagPrefix( " my.ComBox " ,  " ylj " )] 
namespace  my.ComBox
... {
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:ComBox runat=server>")]
    public class ComBox : WebControl,ICallbackEventHandler
    ...{
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public override string ID
        ...{
            get
            ...{
                return base.ID;
            }
            set
            ...{
                base.ID = value;
            }
        }
        /**////

        /// 获取用户选择内容
        ///

        public string Text
        ...{
            get
            ...{
                String s = (String)ViewState["Text"];
                return ((s == null) ? String.Empty : s);
            }

            set
            ...{
                ViewState["Text"] = value;
            }
        }
        /**//// 

        /// 是否允许用户输入值,为使控件既可以同过选择值，又可以通过用户输入设置此属性。
        /// 

        public bool AllowWrite
        ...{
            get
            ...{
                if (ViewState["AllowWrite"] == null)
                ...{
                    return true;
                }
                else
                ...{
                    return (bool)ViewState["AllowWrite"];
                }
            }
            set 
            ...{
                ViewState["AllowWrite"] = value;
            }
        }
        /**//// 

        ///  生成ComBoxItem的值
        /// 

        public string ItemsValue
        ...{
            get
            ...{
                if (ViewState["ItemValue"] == null)
                ...{
                    return "";
                }
                else
                ...{
                    return ViewState["ItemValue"].ToString();
                }
            }
            set
            ...{
                ViewState["ItemValue"] = value;
            }
        
        }
        /**//// 

        /// 设置控件的宽度
        /// 

        public override Unit Width
        ...{
            get
            ...{
                if(ViewState["Width"]==null)
                ...{
                    return base.Width;
                }
                else
                ...{
                    return (Unit)ViewState["Width"];
                }
            }
            set
            ...{
                ViewState["Width"] = value;
            }
        }
        /**//// 

        /// 样式表和js文件的所在路径
        /// 

        public string ControlsURL
        ...{
            get
            ...{
                if (ViewState["ControlsURL"] == null)
                ...{
                    return "My Controls/";
                }
                else
                ...{
                    return ViewState["ControlsURL"].ToString();
                }
            }
            set
            ...{
                ViewState["ControlsURL"] = value;
            }
        }
        public string CssStyle
        ...{
            get
            ...{
                if (ViewState["CssStyle"] == null)
                ...{
                    return "Default";
                }
                else
                ...{
                    return ViewState["CssStyle"].ToString();
                }
            }
            set
            ...{
                ViewState["CssStyle"] = value;
            }
        }
        
        public event EventHandler ComBox_Request;
        protected virtual void OnComBox_Request(object sender,EventArgs e)
        ...{ 
            if(ComBox_Request!=null)
            ...{
                ComBox_Request(this, e);
            }
        
        }
        public string  GetCallbackResult()
        ...{ 
            return ItemsValue;
        }
        void ICallbackEventHandler.RaiseCallbackEvent(string eventArgument)
        ...{
            OnComBox_Request(this, EventArgs.Empty);
        }
        
        protected override void  OnPreRender(EventArgs e)
        ...{
            ClientScriptManager curClientScriptManger = Page.ClientScript;
            curClientScriptManger.RegisterClientScriptInclude(this.GetType(), "0", ControlsURL.ToString() + "JS/CreateCombox.js");
            base.OnPreRender(e);
          
        }
        protected override void RenderContents(HtmlTextWriter output)
        ...{
            output.AddAttribute(HtmlTextWriterAttribute.Type, "text/css");
            output.AddAttribute(HtmlTextWriterAttribute.Rel, "stylesheet");
            output.AddAttribute(HtmlTextWriterAttribute.Href, ControlsURL + "Css/ComBox/ComBox.css");
            output.RenderBeginTag(HtmlTextWriterTag.Link);
            output.RenderEndTag();
            output.AddAttribute(HtmlTextWriterAttribute.Type, "Text");
            output.AddAttribute(HtmlTextWriterAttribute.Value, "");
            output.AddAttribute(HtmlTextWriterAttribute.Class, "Combox_"+CssStyle.ToString());
            output.AddAttribute(HtmlTextWriterAttribute.Id, "Textbox_" + ID);
            output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetCallbackEventReference(this, null, "CreatComboBox", "Textbox_" + ID) + ";return false;");
            if ((bool)AllowWrite == true)
            ...{
                output.AddAttribute(HtmlTextWriterAttribute.ReadOnly, "readonly");
            }
            output.RenderBeginTag(HtmlTextWriterTag.Input);
            output.RenderEndTag();
            output.AddAttribute(HtmlTextWriterAttribute.Src, ControlsURL.ToString() + "Css/ComBox/Img/DropArrow.gif");
            output.AddAttribute(HtmlTextWriterAttribute.Class, "BtnImg_"+CssStyle.ToString());
            output.AddAttribute(HtmlTextWriterAttribute.Onclick, Page.ClientScript.GetCallbackEventReference(this, null, "CreatComboBox", "Textbox_" + ID) + ";return false;"); ;
            output.RenderBeginTag(HtmlTextWriterTag.Img);
            output.RenderEndTag();
        }
       
    }
}

具体生成控件并实现功能前台的js脚本代码如下：

 

var  oPopup = window.createPopup();
var  popt = false ;
var  ShowPopupFlag = false ;


function  CreatComboBox(str,obj)
... {
    var Arr=str.split(",");
    var CreateCheckBox = '';
    var TextBox=obj.id;
    var PopTop = getIET(obj)+21;
    var PopLeft=getIEL(obj);
   
    for(var i=0;i<Arr.length;i++)
    ...{
        CreateCheckBox+=""+ i +"" class="ComboBoxItem_Mac" οnmοuseοver='this.className="ComboBoxItemHover_Mac"'  οnmοuseοut='this.className="ComboBoxItem_Mac"'>"+i+" value="+Arr[i]+" οnclick=GetValeu(this) />"+i+"" οnclick=ChangeChildStatus(this.id)>"+Arr[i]+"

"
    }
    
    var styleStr='body{background-image: url(My Controls/Css/ComBox/Img/dropdownBg.gif);border: 1px solid #C3C3C3;border-top: none;    scrollbar-face-color: #F8F6F2;scrollbar-highlight-color: #ffffff;scrollbar-shadow-color:#E9E9E9;scrollbar-3dlight-color:#DBDBDB;scrollbar-arrow-color:#787878;scrollbar-track-color: #F5F5F5;scrollbar-darkshadow-color: #AEAEAE; }.ComboBoxItem_Mac{font-family:Arial;font-size:11px;color:#333333;padding: 0px;text-decoration:none;text-align:left;}.ComboBoxItemHover_Mac{font-family: Arial;font-size:11px; color:white;text-decoration: none;background-color: #777777;cursor: hand;padding: 0px;text-align: left;}';
    
    var HtmlStr=''+styleStr+''+CreateCheckBox+''
    
    oPopup.document.body.innerHTML = "";
    var oPopBody = oPopup.document.body;
    oPopup.show(PopLeft,PopTop, 122, 150, document.body); 
    oPopup.document.write(HtmlStr);
}
function  getIET(e) ... {
var t=e.offsetTop;
while(e=e.offsetParent)...{
t+=e.offsetTop;
}
return t;
}

function  getIEL(e) ... {
var l=e.offsetLeft;
while(e=e.offsetParent)...{
l+=e.offsetLeft;
}
return l;}

前台的样式文件定义如下：

.Combox_Default
{...} {
    background-image: url(Img/bg.gif);
    background-repeat: repeat-x;
    vertical-align: middle;
    font-family: Arial, Verdana;
    border: 0px;
    margin-right: 0px;
    border-left: 1px solid #B3B3B3;
    font-size: 12px;
    color: black;
    padding-top: 0px;
    padding-left: 3px;
    height: 21px;
    width:100px
 }
  .BtnImg_Default
     {...} {
    vertical-align: middle;
    }

 本示例仅仅简单的实现了ComboBox的部分功能，本人希望它还能支持主题皮肤的功能，因此将继续研究下去。