How to: Update List Items

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This programming task shows how to use the UpdateListItems method of the Lists Web service to update items in a list through a Microsoft Windows application.

Use a System.Xml.XmlElement object to create a Batch element in Collaborative Application Markup Language (CAML) that can contain multiple Method elements, and use the UpdateListItems method to post the methods and update items. The Cmd attribute of each Method element determines the operation that is performed on an item by specifying one of the following values:

• Delete -- Delete an item.

• New -- Create an item.

• Update -- Modify an item.

Procedures

Before you begin, create a Windows application as described in Getting Started with Programmatically Customizing a SharePoint Web Site in Visual Studio. For information about setting a Web reference to a Windows SharePoint Services Web service, see Web Service Guidelines.

To add code to update list items

1. Open Form1 in Design view, open the Toolbox, and then drag a Button control onto the form.

2. Double-click the Button1 control to display the code editor, and then add the following lines of code to the Click event handler:

   'Declare and initialize a variable for the Lists Web service.
   Dim listService As New sitesWebServiceLists.Lists()
   
   'Authenticate the current user by passing their default
   'credentials to the Web service from the system credential cache.
   listService.Credentials = System.Net.CredentialCache.DefaultCredentials
   
   'Set the Url property of the service for the path to a subsite.
   listService.Url = "http://MyServer/sites/MySiteCollection/_vti_bin/Lists.asmx"
   
   'Get Name attribute values (GUIDs) for list and view. 
   Dim ndListView As System.Xml.XmlNode = listService.GetListAndView("MyList", "")
   Dim strListID As String = ndListView.ChildNodes(0).Attributes("Name").Value
   Dim strViewID As String = ndListView.ChildNodes(1).Attributes("Name").Value
   
   'Create an XmlDocument object and construct a Batch element and its 'attributes. Note that an empty ViewName parameter causes the method 'to use the default view. 
   Dim doc As New System.Xml.XmlDocument()
   Dim batchElement As System.Xml.XmlElement = doc.CreateElement("Batch")
   batchElement.SetAttribute("OnError", "Continue")
   batchElement.SetAttribute("ListVersion", "1")
   batchElement.SetAttribute("ViewName", strViewID)
   
   'Specify methods for the batch post using CAML. To update or delete, 'specify the ID of the item, and to update or add, specify 
   'the value to place in the specified columns.
   batchElement.InnerXml = "<Method ID='1' Cmd='Update'>" +
      "<Field Name='ID'>6</Field>" +
      "<Field Name='Title'>Modified sixth item</Field></Method>" +
      "<Method ID='2' Cmd='Update'><Field Name='ID'>7</Field>" +
      "<Field Name='Title'>Modified seventh item</Field></Method>" +
      "<Method ID='3' Cmd='Delete'><Field Name='ID'>5</Field>" +
      "</Method><Method ID='4' Cmd='New'>" +
      "<Field Name='Title'>Added item</Field></Method>"
   
   'Update list items. This example uses the list GUID, which is recommended, but the list display name will also work.
   listService.UpdateListItems(strListID, batchElement)
   

   /*Declare and initialize a variable for the Lists Web service.*/
   sitesWebServiceLists.Lists listService = new sitesWebServiceLists.Lists();
   
   /*Authenticate the current user by passing their default
   credentials to the Web service from the system credential cache.*/
   listService.Credentials =
   System.Net.CredentialCache.DefaultCredentials;
   
   /*Set the Url property of the service for the path to a subsite.*/
   listService.Url = "http://MyServer/sites/MySiteCollection/_vti_bin/Lists.asmx";
   
   /*Get Name attribute values (GUIDs) for list and view. */
   System.Xml.XmlNode ndListView = listService.GetListAndView("MyList", "");
   string strListID = ndListView.ChildNodes[0].Attributes["Name"].Value;
   string strViewID = ndListView.ChildNodes[1].Attributes["Name"].Value;
   
   /*Create an XmlDocument object and construct a Batch element and its attributes. Note that an empty ViewName parameter causes the method to use the default view. */
   System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
   System.Xml.XmlElement batchElement = doc.CreateElement("Batch");
   batchElement.SetAttribute("OnError", "Continue");
   batchElement.SetAttribute("ListVersion", "1");
   batchElement.SetAttribute("ViewName", strViewID);
   
   /*Specify methods for the batch post using CAML. To update or delete, specify the ID of the item, and to update or add, specify 
   the value to place in the specified column.*/
   batchElement.InnerXml = "<Method ID='1' Cmd='Update'>" +
      "<Field Name='ID'>6</Field>" +
      "<Field Name='Title'>Modified sixth item</Field></Method>" +
      "<Method ID='2' Cmd='Update'><Field Name='ID'>7</Field>" +
      "<Field Name='Title'>Modified seventh item</Field></Method>" +
      "<Method ID='3' Cmd='Delete'><Field Name='ID'>5</Field>" +
      "</Method><Method ID='4' Cmd='New'>" +
      "<Field Name='Title'>Added item</Field></Method>";
   
   /*Update list items. This example uses the list GUID, which is recommended, but the list display name will also work.*/
   try
   {
      listService.UpdateListItems(strListID, batchElement);
   }
   catch (SoapServerException ex)
   {
      MessageBox.Show(ex.Message);
   }
   

   Note

   Posting the UpdateListItems method silently fails if a specified item does not exist. The ID for a deleted item is maintained after a delete operation. Consequently, the example deletes the fifth item in the list, but 5 is not reassigned as the ID for another item.

3. On the Debug menu click Start Debugging, or press F5, to test the form.