-----------------------------------------------DDL的载入就激发的方法-------------------------------------

    protected void Page_Load(object sender, EventArgs e)

    {

        DropDownList1_SelectedIndexChanged(sender, e);

    }

 -----------------如果绑定的数据里没有此选项，那么Bind()就会导致一个错误，如何避免呢？ ----------------------

                         ListItem li = DDLInvoiceType.Items.FindByValue("Value") as ListItem;                          if (li != null)                          {
                                   li.Selected = true;                          }else li.SelectedIndex=-1;

法二：

DropDownList1.SelectedIndex = DropDownList1.Items.IndexOf(DropDownList1.Items.FindByValue("Value值")); 就是如果通过FindByValue没有找到指定项则为null，而Items.IndexOf(null)会返回-1.

------------------------------------------------------------------------------------------------------

DDL的设置初始选定项:

DDL.Items.FindByValue("初始选定项").Selected=true;

或者 DDL.Items.FindByText("初始选定项").Selected=true;

DDL.SelectedIndex=DDL.Items.IndexOf(DDL.Items.FindByValue("初始选定项"));

或者 DDL.SelectedIndex=DDL.Items.IndexOf(DDL.Items.FindByText("初始选定项"));

 

DDL的各种绑定方式:

一、在页面初始化时候将集合绑定到DropDownList

public void Page_Load(Object src.EventArgs e)

{

ArrayList arrValue = new ArrayList();

arrValue.add("kk");

arrValue.add("dd");

arrValue.add("aa");

arrValue.add("cc");

//将数组绑定到DropDownList控件的DataSource属性

ddl.DataSource = arrValue;

ddl.DataBind();

}

//实现

选项有:<asp:DropDownList id="ddl" runat="server"/>

二、在页面初始化的时候向DropDownList添加数据public void Page_Load(Object src.EventArgs e)

{

ddl.Items.Add(new ListItem("text","value");

ddl.Items.Add(new ListItem("text1","value1");

ddl.Items.Add(new ListItem("text2","value2");

}

//实现

选项有:<asp:DropDownList id="ddl" runat="server"/>

三、将DataReader读取的数据动态绑定到DropDownList

protected void Page_Load(object sender, EventArgs e)

{

if (!Page.IsPostBack)

{

string myconnstr="Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+Server.MapPath(".")+"..\\database\\db.mdb";

OleDbConnnection myconn=new OleDbConnnection(myconnstr);

string sqlstr="select * from test";

OleDbCommand myComm = new OleDbCommand(sqlstr,myconn);

myComm.Connection.Open();

OleDbDataReader dr=myComm.ExecuteReader();

while (dr.Read())

{

bj.Items.Add(new ListItem(dr["bjmc"].ToString(), dr["id"].ToString()));//增加Item

//或者这样也能绑定，

//DropDownList1.Items.Add( new ListItem( myReader[1].ToString(),myReader[0].ToString() ) );//增加Item

//都是要在知道Sql语句或者数据表结构的前提下才能这样绑定

}

dr.Close();

}

}

四、将DataSet读取的数据动态绑定到DropDownList

SqlConnection sqlconn = new SqlConnection();

sqlconn.ConnectionString = "workstation id=localhost;packet size=4096;user

id=sa;data source=db1;persist security info=False;initial catalog=DB";

sqlconn.Open();

SqlDataAdapter sqldar = new SqlDataAdapter("select UserID,UserName from forums_Users",sqlconn);

sqldar.SelectCommand.CommandType = CommandType.Text;

DataSet Ds= new DataSet();

sqldar.Fill(Ds,"Users");

ddl.DataSource = Ds.Tables["Users"].DefaultView;

ddl.DataTextField="UsersName";

ddl.DataValueField ="UserID";

ddl.DataBind();

sqlconn.Close();

五、使用DataBinder.Eval(Container.DataItem,"表字段")输出绑定数据protected void Page_Load(object sender, EventArgs e)

{

if (!Page.IsPostBack)

{

string myconnstr="Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+Server.MapPath(".")+"..\\database\\db.mdb";

OleDbConnnection myconn=new OleDbConnnection(myconnstr);

string sqlstr="select * from test";

OleDbCommand myComm = new OleDbCommand(sqlstr,myconn);

myComm.Connection.Open();

OleDbDataReader dr=myComm.ExecuteReader();

ddl.DataSource = dr;

ddl.DataBind(); 绑定倒DD1中

}

}

在UI界面的DDL中直接调用，绑定的方法调用

DataBinder.Eval(Container.DataItem,"表字段")