我想从DropDownList1下(A,B,C)中选择其中一个条件进行查询,然后查询结果显示在GridView1里,如何设置查询按纽?请大狭们指教,小弟在线等待...

难道都没人会吗?请版主帮我解决,小弟一直在线等待中....[Discuz!]&Menu=yes" target="_blank">" border="0">

string Sqlstr = "select * from table where 1=1 ";
        if (this.TextBox1.Text.Trim() != "")
        {
            Sqlstr += "and UserID like '%" + TextBox1.Text.ToString() + "%'";
        }
        if (this.TextBox2.Text.Trim().ToString() != "")
        {
            string Emno1 = this.TextBox2.Text.Trim();
            Sqlstr += "and Emno='" + this.TextBox2.Text.Trim() + "'";
        }
        if (this.TextBox3.Text.Trim() != "")
        {
            Sqlstr += "and Extphone =  '" + TextBox3.Text.Trim().ToString() + "'";
        }

string str = DropDownList1.SelectedItem.Text;
        string sql = "select * from table ";
        //存放数据库的联机字符串
        string connStr;
        //建立OleDbConnection对象并指定其数据库的联机字符串
        OleDbConnection myConnection;
        //建立名称为myDataSet的确良DataSet对象,以及声明myAdapter是一个DataAdapter对象
        DataSet myDataSet;
        OleDbDataAdapter myAdapter;
        switch (str)
        {
            case A:
                sql += "where 条件A";
                break;
            case B:
                sql += "where 条件B";
                break;
            case C:
                sql += "where 条件C";
                break;

        }
        //存放数据库的联机字符串------------Access数据库
        connStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=";
        //数据库所在的真实路径.
        connStr += Server.MapPath("book.mdb"); //将指定数据库的URL地址转成真实路径

        //建立OleDbConnection对象并指定其数据库的联机字符串
        myConnection = new OleDbConnection(connStr);

        //建立名称为myDataSet的确良DataSet对象,以及声明myAdapter是一个DataAdapter对象
        myDataSet = new DataSet();

        //建立myAdapter对象并指定所要执行的SQL命令及要联机的数据库
        myAdapter = new OleDbDataAdapter(sql, myConnection);

        //用fill方法将查询结果放到DataSet对象中
        myAdapter.Fill(myDataSet, "book");


        //让DataGrid控件显示该DataTable对象中的所有数据
        GridView1.DataSource = myDataSet;
        GridView1.DataBind();