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10月26日

If you can get your recordset into a list you can use LINQ like so:

HTML
<asp:ListView ID="ListView1" runat="server">
         <LayoutTemplate>
                <asp:PlaceHolder runat="server" ID="itemPlaceHolder"></asp:PlaceHolder>
         </LayoutTemplate>
         <ItemTemplate>
                <table>
                     <tr>
                         <td><%#Eval("Key")%></td>
                     </tr>
                     <tr>
                         <td>
                             <ol>
                                <asp:ListView ID="ListView2" runat="server" DataSource='<%# Eval("emps") %>' >
                                      <LayoutTemplate>
                                            <asp:PlaceHolder runat="server" ID="itemPlaceHolder"></asp:PlaceHolder>
                                      </LayoutTemplate>
                                      <ItemTemplate>
                                             <li><%#Eval("Name")%></li>
                                      </ItemTemplate>
                                </asp:ListView>
                            </ol>
                        </td>
                    </tr>
               </table>
               <hr />
          </ItemTemplate>
</asp:ListView>

Code Behind
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

          Dim empsByLocation = _
                  From em In Employee.getEmployees() _
                  Group em By Key = em.Location Into Group _
                  Select New With {.Key = Key, .emps = Group}          ListView1.DataSource = empsByLocation
          ListView1.DataBind()
End Sub

My Employee Class
Public Class Employee

      Public _Location As String
      Public _Name As String
      Public _Phone As String
      Public _ID As Long

      Public Sub New(ByVal ID As Long, ByVal Name As String, ByVal Phone As String, ByVal Location As String)
           Me._Location = Location
           Me._Name = Name
           Me._Phone = Phone
           Me._ID = ID
      End Sub

      Public ReadOnly Property Name() As String
          Get
               Return _Name
          End Get
      End Property      Public ReadOnly Property Location() As String
         Get
              Return _Location
         End Get
      End Property

      Public Shared Function getEmployees() As List(Of Employee)

            Dim employees As New List(Of Employee)

            employees.Add(New Employee(1, "Bob", "09809809", "California"))
            employees.Add(New Employee(2, "Jack", "3453465", "California"))
            employees.Add(New Employee(3, "Arnold", "7899878978", "California"))
            employees.Add(New Employee(4, "Barry", "2134678", "Arizona"))
            employees.Add(New Employee(5, "Titch", "454458", "Arizona"))
            employees.Add(New Employee(6, "Mick", "23432424", "Arizona"))

            Return employees
     End Function End Class

Will produce the output:

California

Bob
Jack
Arnold

Arizona

Barry
Titch
Mick

You can tidy it up but I hope this was what you were after.

20:43 | 添加评论 | 固定链接 | 写入日志 | Code

C# Reoeat Repeater

Imagine that you have a database table named Players with a list of basketball players from the NBA. The schema for this table might look as follows:

`Players`
`FullName`	`varchar(50)`
`Team`	`varchar(20)`

Improving the Data Model...

The schema for the Players table is extremely simple and far from ideal. If this were a "real" database application, we'd likely have a plethora of additional attributes for a player. Also, we'd likely want a PlayerID primary key field to uniquely identify each player (since a player's name is not a guarantee unique attribute). Furthermore, we'd likely have a separate table to store information about each NBA team, and then have the Team attribute in the Players table be a foreign key.

Given this table schema, imagine that we have the following records:

Shaq, Lakers
Rick Fox, Lakers
Vlade Divac, Kings
Tim Duncan, Spurs
Kobe Bryan, Lakers
Terry Parker, Spurs
Robert Horry, Lakers
Chris Webber, Kings
Mike Bibby, Kings
David Robinson, Spurs
Doug Christie, Kings

Now, imagine that you wanted to display the NBA players such that the players for each team were grouped together. Clearly, a simple SQL query with an appropriate ORDER BY clause will get all of the players ordered by team. That is, the following query:

SELECT FullName, Team
FROM Players
ORDER BY Team

Will return all the players playing for the Kings, followed by all the players playing for the Lakers, followed by all the players playing for the Spurs. Specifically, the results of the above SQL query, when run on the sample data, will be as follows:

Vlade Divac, Kings
Chris Webber, Kings
Mike Bibby, Kings
Doug Christie, Kings
Shaq, Lakers
Rick Fox, Lakers
Kobe Bryan, Lakers
Robert Horry, Lakers
Tim Duncan, Spurs
Terry Parker, Spurs
David Robinson, Spurs

Therefore, we could have a DataGrid display the name of each player, followed by their team name. However, what if we wanted the display to be a bit different. Rather than blandly list each player and his associated team, we want to list, in big bold letters, the name of the team, followed by all of its players. That is, we want the results to look something like:

Kings

Vlade Divac

Chris Webber

Mike Bibby

Doug Christie

Lakers

Shaq

Rick Fox

Kobe Bryant

Robert Horry

Spurs

Tim Duncan

Terry Parker

David Robinson

Can we get a DataGrid to render this "style" of output? Sure, if we use a TemplateColumn and a bit of clever programming. We could also obtain such an appearance through the use of a master/detail-type DataGrid, which is discussed in detail in An Extensive Examination of the DataGrid Web Control: Part 14.

In using template, we can implement this sort of display through the use of a DataList and a custom function as well. For this FAQ, let's use the DataList approach.

DataGrid or DataList?

Note that a DataList probably makes more sense here since it is designed for templated columns. Furthermore, the DataList allows for repeated columns via its RepeatColumns property, meaning you could display the teams n to a table column. However, if you need functionality like pagination, then the DataGrid would be a better choice.

Using a DataList to Display the Players, Grouped By Team
Imagine, for a moment, that we only want to display the players for each team, and we're not yet worried about displaying the team name before the list of players. To accomplish this, we could use the following simple DataList:

<asp:DataList runat="server" id="dlPlayers">
<ItemTemplate>
Container.DataItem("FullName")
</ItemTemplate>
</asp:DataList>

This DataList will display a table row and column for each player. Now, to display the team name, we need to be able to determine when the team name switches from one team to the next. That is, when we first start by displaying the players for the Kings, we want to emit the team name Kings and then the player's name, but then for each of the remaining players who play for the Kings, we only want to emit their name. When the first player for the next team (the Lakers) is displayed, again, we want to display both the team name and the player's name; however, for the remaining Lakers players we only want to display the player's name.

In the FAQ, Customizing the Appearance of a DataGrid Column Value, we saw how to use a custom function to output a custom value based on the value of a DataSource field. We'll use this technique in this exercise to emit the player's team name if the team name has switched from a previous value to a new value. This can be accomplished with the following code:

VB.NET

20:37 | 添加评论 | 固定链接 | 写入日志 | Code

C# repeat repeater

The two key templates are the LayoutTemplate and ItemTemplate. The LayoutTemplate specifies the ListView's encasing markup, while the ItemTemplate specifies the markup used to generate each record bound to the ListView. For example, to display an ordered list of items with a ListView, the resulting templates would look like the following:


<asp:ListView ID="..." runat="server" DataSourceID="...">

   <LayoutTemplate>

      <ol>

         <asp:PlaceHolder runat="server" ID="itemPlaceholder"></asp:PlaceHolder>

      </ol>

   </LayoutTemplate>



   <ItemTemplate>

      <li><%# Eval("columnName") %></li>

   </ItemTemplate>

</asp:ListView>

Since the ListView's LayoutTemplate and ItemTemplate are each defined separately, we need some way to tell the LayoutTemplate, "Hey, for each record you are displaying, put the rendered item markup here." This is accomplished by adding a server-side control with the ID value specified by the ListView's ItemPlaceholderID property. This property defaults to a value of "itemPlaceholder", which is why I have named the PlaceHolder control in the LayoutTemplate as such. I could, however, had given the PlaceHolder control an alternate ID, but then I'd need to specify this value in the ListView's ItemPlaceholdID property.

To output a particular field value in the ItemTemplate, use the databinding syntax, <%# Eval("columnName") %>.

Imagine that the above ListView is bound to an employees database table, and that in the ItemTemplate we were rendering the FullName column within the <li> element. What would the ListView's rendered markup look like?

Well, the ListView would start by rendering it's LayoutTemplate:


<ol>

  <asp:PlaceHolder runat="server" ID="itemPlaceholder"></asp:PlaceHolder>

</ol>

It would then render its ItemTemplate for each record bound to the ListView control. This might result in the following markup:


<li>Scott Mitchell</li>

<li>Sam Smith</li>

<li>Jisun Lee</li>

<li>Andrew Fuller</li>

<li>Edgar Johnson</li>

<li>Ellen Plank</li>

The ItemTemplate's rendered markup is put in place of the PlaceHolder control (since its ID matches the ListView's ItemPlaceholderID value. The net result is the following markup:


<ol>

<li>Scott Mitchell</li>

<li>Sam Smith</li>

<li>Jisun Lee</li>

<li>Andrew Fuller</li>

<li>Edgar Johnson</li>

<li>Ellen Plank</li>

</ol>

An Example of Displaying Simple Data with the ListView
An ASP.NET version 3.5 website is available at the end of this article with a demo illustrating the ListView control in action. This demo uses the Microsoft Access Northwind database, which is included in the demo application's App_Data folder. The "Simple Data" demo illustrates how to use the ListView to display records from the Northwind database's Products table. An AccessDataSource control is used to query the Products table and bind the resulting records to the ListView.

In particular, the ListView starts by displaying the title "Product Listing" in an <h3> element. It then lists the products within a <blockquote> element, which has the effect of indenting the output. Each product has its name, category, unit price, and quantity per unit displayed. And each product is separated from one another via a horizontal rule element (<hr>), which is defined in the ItemSeparatorTemplate.

The ListView and AccessDataSource's declarative markup follows:


<asp:ListView ID="ProductList" runat="server" DataSourceID="ProductDataSource">

   <LayoutTemplate>

      <h3>Product Listing</h3>

      <blockquote>

         <asp:PlaceHolder runat="server" ID="itemPlaceholder"></asp:PlaceHolder>

      </blockquote>

   </LayoutTemplate>



   <ItemSeparatorTemplate>

      <hr />

   </ItemSeparatorTemplate>



   <ItemTemplate>

      <h4><%#Eval("ProductName")%> (<%# Eval("CategoryName") %>)</h4>

      Available at <%#Eval("UnitPrice", "{0:c}")%>, 

      with <%#Eval("QuantityPerUnit")%>.

   </ItemTemplate>

</asp:ListView>





<asp:AccessDataSource ID="ProductDataSource" runat="server"

   DataFile="~/App_Data/Northwind.mdb"

   SelectCommand="SELECT [ProductName], [QuantityPerUnit], [UnitPrice], [CategoryName] FROM [Alphabetical List of Products]">

</asp:AccessDataSource>

When this page is visited, the ListView renders into the following HTML:


<h3>Product Listing</h3>

<blockquote>



<h4>Chai (Beverages)</h4>

Available at $18.00, 

with 10 boxes x 20 bags.



<hr />



<h4>Chang (Beverages)</h4>

Available at $19.00, 

with 24 - 12 oz bottles.



<hr />



<h4>Aniseed Syrup (Condiments)</h4>

Available at $10.00, 

with 12 - 550 ml bottles.



<hr />



<h4>Chef Anton's Cajun Seasoning (Condiments)</h4>

Available at $22.00, 

with 48 - 6 oz jars.



<hr />



<h4>Grandma's Boysenberry Spread (Condiments)</h4>

Available at $25.00, 

with 12 - 8 oz jars.



... Many products have been removed for brevity ...



</blockquote>

Which appears in the visitor's browser like so:

The list of products.

Conclusion
The ListView control, new to ASP.NET 3.5, offers the same rich data features found in the GridView, but allows for a much more flexible rendered output. As we saw in this article, the ListView's rendered output is based on the markup, databinding expressions, and Web controls added to its LayoutTemplate and ItemTemplate. There are a number of other templates available, as well, and we will explore these along with features like sorting, paging, deleting, editing, and inserting in future installments of this article series.

Until then... Happy Programming!

20:34 | 添加评论 | 固定链接 | 写入日志 | Code

C# Repeat Repeater

Linq over DataTable.Rows

Currently you can't directly use Linq over and DataSet/DataTable/DataRowCollection/etc. class. Trying something like this won't work:

var q = from r in table.Rows select r;

Enabling Linq over the classes mentioned above is under consideration by Microsoft and I don't doubt they will enable them. But if you wish to do it now, here is the simple workaround. Everything you need to do (the Linq requires) is that the class implements IEnumerable<T>. So, I will create a generic class that wraps around any IEnumerable and implements IEnumerable<DataRow>. Here is the code:

// simple wrapper that implements IEnumerable<T>
internal class LinqList<T>: IEnumerable<T>, IEnumerable
{
IEnumerable items;

internal LinqList(IEnumerable items)
{
this.items = items;
}

#region IEnumerable<DataRow> Members
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
foreach (T item in items)
yield return item;
}

IEnumerator IEnumerable.GetEnumerator()
{
IEnumerable<T> ie = this;
return ie.GetEnumerator();
}
#endregion
}

The code is pretty straightforward, isn't it. And here is a simple test:

// create and fill table
DataTable table = new DataTable();
table.Columns.Add("Id", typeof(int));
table.Rows.Add(new object[]{1});
table.Rows.Add(new object[]{2});
table.Rows.Add(new object[]{3});
// create a wrapper around Rows
LinqList<DataRow> rows = new LinqList<DataRow>(table.Rows);
// do a simple select
IEnumerable<DataRow> selectedRows = from r in rows
where (int)r["Id"] == 2
select r;
// output result
foreach (DataRow row in selectedRows)
Console.WriteLine(row["Id"]);

It is not pretty as it could be but it certainly works. And if you want you can create your own strong typed table implementation that exposes LinqList<DataRow> Rows property. Perhaps using a code generator such as CodeSmith instead of doing boring work yourself.

Published 15. januar 2006 23:25 by Miha Markic

Filed under: .net

Comments

# re: Linq over DataTable.Rows

30. januar 2006 14:36 by Sahil Malik

I like that "LinqList" :)

# re: Linq over DataTable.Rows (Error FrameW 2.0)

3. februar 2006 8:38 by Dln

The non-generic type 'System.Collections.IEnumerable' cannot be used with type arguments

on word -'IEnumerable<t>' ???</t>

# re: Linq over DataTable.Rows

4. februar 2006 0:46 by Miha Markic

Hi Din,

Did you include System.Collections.Generic namespace? Anyway, check out Sahil's solution, too.

20:30 | 添加评论 | 固定链接 | 写入日志 | Code

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asp.net

C# repeat Repeater

C# Reoeat Repeater

C# repeat repeater

C# Repeat Repeater

Linq over DataTable.Rows

Comments

# re: Linq over DataTable.Rows

# re: Linq over DataTable.Rows (Error FrameW 2.0)

# re: Linq over DataTable.Rows