学步园

最近在项目中处理一个winForm中设定ComboBox值，奇怪的是用一个对象匹配ComboBox的Datasource集合的一个对象时，设置SelectedValue时，竟然得到SelectedValue为null。

网上搜索一下，有说是如果用DateSet绑定时，SelectedValue得到的是null或DataRowView。

后来反复实践，发现可以用以下方法实现：

private void SetValueByItem()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedItem = ac.FindAll(delegate(Area ar) { return ar.Area_ID == a.Area_ID; })[0];<br /> lbResult.Text = cbList.SelectedItem.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }

其他两种设置方式：

private void SetValueByValue()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedValue = a.Area_ID;<br /> lbResult.Text = cbList.SelectedValue.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }

private void SetValueByText()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedIndex = cbList.FindString(a.Area_Name);<br /> lbResult.Text = cbList.SelectedValue.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }

完整代码：

using System;<br /> using System.Collections.Generic;<br /> using System.ComponentModel;<br /> using System.Data;<br /> using System.Drawing;<br /> using System.Text;<br /> using System.Windows.Forms;<br /> namespace WinFormCombobox<br /> {<br /> public partial class frmMain : Form<br /> {<br /> public frmMain()<br /> {<br /> InitializeComponent();<br /> }<br /> #region Members<br /> AreaLists ac;<br /> public AreaLists GetTestArea()<br /> {<br /> AreaLists al = new AreaLists();<br /> for (int i = 1; i < 11; i++)<br /> {<br /> Area a = new Area();<br /> a.Area_ID = i.ToString();<br /> a.Area_Name = "第" + i.ToString() + "名";<br /> al.Add(a);<br /> }<br /> return al;<br /> }<br /> #endregion<br /> #region Events<br /> private void frmMain_Load(object sender, EventArgs e)<br /> {<br /> ac = GetTestArea();<br /> cbList.DataSource = ac;<br /> cbList.DisplayMember = "Area_Name";<br /> cbList.ValueMember = "Area_ID";<br /> }<br /> private void btnSetCombobox_Click(object sender, EventArgs e)<br /> {<br /> ////SetValue0();<br /> //SetValueByValue();<br /> ////SetValueByItem();<br /> SetValueByText();<br /> }<br /> #endregion<br /> #region Methods<br /> private void SetValue0()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.DataSource = GetTestArea();<br /> cbList.DisplayMember = "Area_Name";<br /> cbList.ValueMember = "Area_ID";<br /> cbList.SelectedValue = a.Area_ID;<br /> lbResult.Text = cbList.SelectedValue.ToString();<br /> }<br /> private void SetValueByValue()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedValue = a.Area_ID;<br /> lbResult.Text = cbList.SelectedValue.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }<br /> private void SetValueByItem()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedItem = ac.FindAll(delegate(Area ar) { return ar.Area_ID == a.Area_ID; })[0];<br /> lbResult.Text = cbList.SelectedItem.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }<br /> private void SetValueByText()<br /> {<br /> Area a = new Area();<br /> a.Area_ID = "8";<br /> a.Area_Name = "第8名";<br /> cbList.SelectedIndex = cbList.FindString(a.Area_Name);<br /> lbResult.Text = cbList.SelectedValue.GetType().ToString() + ":" + cbList.SelectedValue.ToString();<br /> }<br /> #endregion<br /> }<br /> }</p> <p>using System;<br /> using System.Collections.Generic;<br /> using System.Text;<br /> namespace WinFormCombobox<br /> {<br /> #region Area<br /> public class Area<br /> {<br /> private string m_Area_ID;<br /> public string Area_ID<br /> {<br /> get { return m_Area_ID; }<br /> set { m_Area_ID = value; }<br /> }<br /> private string m_Area_Name;<br /> public string Area_Name<br /> {<br /> get { return m_Area_Name; }<br /> set { m_Area_Name = value; }<br /> }<br /> private double m_Area_Order;<br /> public double Area_Order<br /> {<br /> get { return m_Area_Order; }<br /> set { m_Area_Order = value; }<br /> }<br /> }<br /> #endregion<br /> [Serializable]<br /> public class AreaLists : List<Area><br /> {<br /> private int _maxItems = 0;<br /> public int MaxItems { get { return this._maxItems; } set { this._maxItems = value; } }<br /> }<br /> }<br />

邀月注：本文版权由邀月和CSDN共同所有，转载请注明出处。

助人等于自助!   3w@live.cn