写了一个能设置ListItem颜色的DropDownList控件

  1using System;
  2using System.Web;
  3using System.Web.UI;
  4using System.Collections;
  5using System.Web.UI.WebControls;
  6
  7
  8namespace SunY.Web.UI.WebControls
  9{
 10    [ToolboxData("<{0}:DropDownList runat=\"server\"></{0}:DropDownList>")] 
 11    public class DropDownList : System.Web.UI.WebControls.DropDownList
 12    {
 13        private ArrayList m_Items;
 14
 15        protected override object SaveViewState() 
 16        { 
 17            ArrayList alstViewState = new ArrayList(); 
 18            object objBaseVS = base.SaveViewState(); 
 19            alstViewState.Add(objBaseVS); 
 20            alstViewState.Add(m_Items); 
 21
 22            return alstViewState; 
 23        } 
 24 
 25
 26        protected override void LoadViewState(object savedState) 
 27        { 
 28            if ( savedState != null ) 
 29            { 
 30                ArrayList alstViewState = (ArrayList)savedState; 
 31                if ( alstViewState.Count >= 1 ) 
 32                { 
 33                    base.LoadViewState(alstViewState[0]); 
 34                } 
 35                if ( alstViewState.Count == 2 ) 
 36                { 
 37                    m_Items = (ArrayList)alstViewState[1]; 
 38                } 
 39            } 
 40        } 
 41
 42
 43        protected override void OnPreRender(EventArgs e)
 44        {
 45            base.OnPreRender (e);
 46
 47            if(m_Items == null)
 48            {
 49                m_Items = new ArrayList();
 50            }
 51
 52            bool IsChange = false;
 53
 54            if(m_Items.Count == this.Items.Count)
 55            {
 56                for(int i = 0; i < this.Items.Count; i++)
 57                {
 58                    sListItem sli = new sListItem(this.Items[i]);
 59                    if(!((sListItem)m_Items[i]).Equals(sli))
 60                    {
 61                        IsChange = true;
 62                        break;
 63                    }
 64                }
 65            }
 66            else
 67            {
 68                IsChange = true;
 69            }
 70
 71            if(IsChange)
 72            {
 73                m_Items.Clear();
 74
 75                ArrayList newList = new ArrayList();
 76
 77                foreach(ListItem li in this.Items)
 78                {
 79                    sListItem sli = new sListItem(li);
 80
 81                    m_Items.Add(sli);
 82                }    
 83            }
 84            
 85
 86        }
 87
 88
 89        protected override void RenderContents(HtmlTextWriter writer)
 90        {
 91            if(m_Items != null && this.Items != null)
 92            {
 93                if(this.Items.Count == m_Items.Count)
 94                {
 95                    bool selected = false;
 96
 97                    for(int i = 0; i < this.Items.Count; i++)
 98                    {
 99                        writer.WriteBeginTag("option");
100
101                        if (this.Items[i].Selected)
102                        {
103                            if (selected)
104                            {
105                                throw new HttpException("Cannot multiselect in DropDownList.");
106                            }
107
108                            selected = true;
109                            writer.WriteAttribute("selected", "true", false);
110                        }
111
112                        writer.WriteAttribute("value", this.Items[i].Value, true);
113
114                        string styleValue = String.Empty;
115
116                        foreach(ItemStyle s in ((sListItem)m_Items[i]).ItemStyles)
117                        {
118                            styleValue += String.Concat(s.Key, ":", s.KeyValue, ";"); 
119                        }
120
121                        writer.WriteAttribute("style", styleValue, false);
122
123                        this.Items[i].Attributes.Render(writer); 
124                        writer.Write('>');
125                        HttpUtility.HtmlEncode(this.Items[i].Text, writer);
126                        writer.WriteEndTag("option");
127                        writer.WriteLine();
128                    }
129                }
130            }
131        }
132    }
133
134    [Serializable]
135    class ItemStyle
136    {
137        private string key;
138        private string keyValue;
139
140        public string Key
141        {
142            get
143            {
144                return key;
145            }
146            set
147            {
148                key = value;
149            }
150        }
151
152        public string KeyValue
153        {
154            get
155            {
156                return keyValue;
157            }
158            set
159            {
160                keyValue = value;
161            }
162        }
163
164        public ItemStyle(string key, string kvalue)
165        {
166            this.key = key;
167            this.keyValue = kvalue;
168        }
169    }
170
171    
172    [Serializable]
173    class sListItem
174    {
175        private string _text;
176        private string _value;
177        private bool _selected;
178        private ArrayList _itemStyle;
179
180        public string Text
181        {
182            get
183            {
184                return _text;
185            }
186            set
187            {
188                _text = value;
189            }
190        }
191
192
193        public string Value
194        {
195            get
196            {
197                return _value;
198            }
199            set
200            {
201                _value = value;
202            }
203        }
204
205
206        public ArrayList ItemStyles
207        {
208            get
209            {
210                return _itemStyle;
211            }
212            set
213            {
214                _itemStyle = value;
215            }
216        }
217
218
219        public bool Selected
220        {
221            get
222            {
223                return _selected;
224            }
225            set
226            {
227                _selected = value;
228            }
229        }
230
231
232        public sListItem()
233        {
234            _text = String.Empty;
235            _value = String.Empty;
236            _itemStyle = new ArrayList();
237            _selected = false;
238        }
239        
240
241        public sListItem(ListItem li)
242        {
243            this.Text = li.Text;
244            this.Value = li.Value;
245            this.Selected = li.Selected;
246            this._itemStyle = new ArrayList();
247            
248            foreach(string key in li.Attributes.CssStyle.Keys)
249            {
250                ItemStyle style = new ItemStyle(key, li.Attributes.CssStyle[key]);
251                this._itemStyle.Add(style);
252            }
253        }
254
255
256        public virtual bool Equals(sListItem item)
257        {
258            if(this.Text == item.Text && this.Value == item.Value)
259            {
260                return true;
261            }
262
263            return false;
264        }
265
266    }
267}
268