You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You create a Web form that contains the following code fragment：  
<asp：TextBox runat="server" ID="txtSearch" />  
<asp：Button runat="server" ID="btnSearch"
Text="Search" OnClick="btnSearch_Click" />  
<asp：GridView runat="server" ID="gridCities" />   
You write the following code segment in the code-behind file：  
01 protected void Page_Load（object sender， EventArgs e）  
02 {  
03   DataSet objDS = new DataSet（）；  
04   SqlDataAdapter objDA = new SqlDataAdapter（objCmd）；  
05   objDA.Fill（objDS）；  
06   gridCities.DataSource = objDs；  
07   gridCities.DataBind（）；  
08   Session["ds"] = objDS；  
09 }  
10 protected void btnSearch_Click（object sender， EventArgs e）  
11 {  
12 ► 
13 }   
You need to ensure that when the btnSearch Button control is clicked， the records in the gridCities GridView control are filtered by using the value of the txtSearch TextBox. Which code segment you should insert at line 12？（）

You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You write the following code segment in the code-behind file to create a Web form：  
01 string strQuery = "select * from Products；"  
02   + "select * from Categories"；  
03 SqlCommand cmd = new SqlCommand（strQuery， cnn）；  
04 cnn.Open（）；  
05 SqlDataReader rdr = cmd.ExecuteReader（）；  
06 ► 
07 rdr.Close（）；  
08 cnn.Close（）；   
You need to ensure that the gvProducts and gvCategories GridView controls display the data that is contained in the following two database tables： the Products database table the Categories database table  
Which code segment should you insert at line 06？（）