asp.net 2.0中gridview里嵌套dropdownlist

在asp.net 2.0中,在一个gridview里,可以嵌套进一个dropdownlist,这是十分容易的事情,而这里讲的是,
在每个dropdownlist里,都绑定的是不同的内容,比如在northwind数据库中,可以用GRIDVIEW显示出
每个category类别,同时每一行的category类别里可以已dropdonwlist下拉框的形式,列出该分类下的所有
产品.下面介绍实现的方法

首先是页面部分的代码
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" OnRowDataBound="GridView1_RowDataBound" >
<Columns>

<asp:BoundField DataField="CategoryID" HeaderText="CategoryID" />
<asp:BoundField DataField="CategoryName" HeaderText="Category Name" />

<asp:TemplateField HeaderText="Category Name">
<ItemTemplate>
<asp:DropDownList ID="DropDownList2" runat="server"></asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>

<asp:TemplateField HeaderText="Products">
<ItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server"></asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>

</Columns>
</asp:GridView>

在codebehind部分,
protected void Page_Load(object sender, EventArgs e)
{
GridView1.DataSource = GetDataSet().Tables[1];//取第二张表Catagories的数据
GridView1.DataBind();
}
//取了二张表，第一张Products 第二张Categories
private DataSet GetDataSet()
{
string query = @"Select p.CategoryID,p.ProductID, p.ProductName FROM Products p
Select c.CategoryID,c.CategoryName FROM Categories c";
string connectionString = ConfigurationManager.ConnectionStrings["northwindconnstr"].ToString();
SqlConnection myConnection = new SqlConnection(connectionString);
SqlDataAdapter ad = new SqlDataAdapter(query, myConnection);
DataSet ds = new DataSet();
ad.Fill(ds);
return ds;
}
在上面的代码中,首先我们通过典型的dataset返回,绑定到gridview上去,注意这里sql语句里有两句,第一句是返回产品,第二句是返回所有的类别category,而在绑定gridview时,我们用
GridView1.DataSource = GetDataSet().Tables[1];,将第一个table表里的category记录绑定到gridview里去,接下来,我们要处理模版列中的dropdownlist了，这个可以在row_databound事件中写入代码,如下
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
DataTable myTable = new DataTable();
DataColumn productIDColumn = new DataColumn("ProductID");
DataColumn productNameColumn = new DataColumn("ProductName");
myTable.Columns.Add(productIDColumn);
myTable.Columns.Add(productNameColumn);
DataSet ds = new DataSet();
ds = GetDataSet();
int categoryID = 0;
string expression = String.Empty;
if (e.Row.RowType == DataControlRowType.DataRow)
{
categoryID = Int32.Parse(e.Row.Cells[0].Text);
expression = "CategoryID = " + categoryID;
//找到每一行里的dropdownlist
DropDownList ddl = (DropDownList)e.Row.FindControl("DropDownList1");
//把products表中，对应CategoryID = XX 的记录选出来,并加入MyTable里
DataRow[] rows = ds.Tables[0].Select(expression);
foreach (DataRow row in rows)
{
DataRow newRow = myTable.NewRow();
newRow["ProductID"] = row["ProductID"];
newRow["ProductName"] = row["ProductName"];
myTable.Rows.Add(newRow);
}
ddl.DataSource = myTable;
ddl.DataTextField = "ProductName";
ddl.DataValueField = "ProductID";
ddl.DataBind();
//处理DropDownList2
myTable = ds.Tables[1];//把第二张表提出来
DropDownList dd2 = (DropDownList)e.Row.FindControl("DropDownList2");
dd2.DataSource = myTable;
dd2.DataTextField = "CategoryName";
dd2.DataValueField = "CategoryID";
dd2.DataBind();
for (int i = 0; i < dd2.Items.Count; i++) {
if (Convert.ToInt32(dd2.Items[i].Value) == categoryID)
{
dd2.Items[i].Selected = true;
}
else {
dd2.Items[i].Selected = false;
}
}
}
}
这里的原理大致如下:
首先，我们建立了一个datatable,包含了productid,productname列,然后将其与 gridview绑定,之后再用
categoryID = Int32.Parse(e.Row.Cells[0].Text);

expression = "CategoryID = " + categoryID;
构造一个筛选表达式,这里指定为categoryID,然后通过
DropDownList ddl = (DropDownList)e.Row.FindControl("DropDownList1");
DataRow[] rows = ds.Tables[0].Select(expression);
,找出符合其类别等于某一categoryID的所有产品,这里构造出datarow集合了,最后,使用循环
,将某类别下的产品全部添加到datatable中去,最后将datatable和dropdownlist绑定,就实现功能了