Updating Property Values

Look at the grid. Properties whose values we can modify using the PAPI have a CanWrite property value of true.

So far, we have only been reading property values and using Web Author to update them. Let’s attempt to change the Description property value using the PAPI.

We are going to keep it really simple and update only one property: the Description. You might find it a useful exercise to go ahead and add more textboxes to the page to update the other writable properties of the channel item object, like its Name, DisplayName, StartDate, ExpiryDate fields, etc.

In HTML view, add the code shown below (including the text markers) above the opening <asp:DataGrid> tag:

<p>
  <table>
  <tr>
    <td>Description:</td>
    <td>(Add the text box for the Description here)</td>
  </tr>
  <tr>
    <td colspan="2" align="right">
      (Add the Update button here)
      <INPUT type="button" value="Close" onclick="javascript:window.close();">
    </td>
  </tr>
  </table>
  (Add the Label for displaying error messages here)
</p>

Toggle to Design view. Drag and drop the following controls from the Web Forms section of the Toolbox and delete all text markers. We will be adding a textbox for entering the channel item’s new description, a button for saving it, and a label for showing error messages (if there are any). Arrange them as shown in the diagram below and set their properties accordingly.

Control	Property	Property Value
TextBox	ID Rows TextMode	txtDescription 3 MultiLine
Button	ID Text	btnUpdate Update
Label	ID Text	lblErrorMessage (empty string)

In the Page_Load() event handler, add code to read the Description of the current hierarchy item and display it on the screen.

private void Page_Load(object sender, System.EventArgs e)
{
  // Put user code to initialize the page here
  CmsHttpContext cmsContext = CmsHttpContext.Current;
  hItem = null;

  string cmsObjectGuid = "";
  if (Request.QueryString["CMSObjectGuid"] != null)
  {
    // template gallery items and resource gallery items
    cmsObjectGuid = Request.QueryString["CMSObjectGuid"];
    hItem = cmsContext.Searches.GetByGuid(cmsObjectGuid);
  }
  else
  {
    // channels and postings
    hItem = cmsContext.ChannelItem;
  }

  // list all properties and their values in the grid
  if (hItem != null)
  {
    litCurrentItem.Text = hItem.Path;
    if (!Page.IsPostBack)
					{
					txtDescription.Text = hItem.Description;
					}
    ListProperties();
  }
}

Toggle to Design mode and double-click on the btnUpdate button. In the btnUpdate_OnClick() event handler, we will write the code that updates the Description property value of the HierarchyItem based on the text entered into the textbox.

private void btnUpdate_Click(object sender, System.EventArgs e)
{
  try
					{
					// IMPORTANT: You must be in update mode for the code to work
					// update the description
					hItem.Description = txtDescription.Text;
					// commit the change
					CmsHttpContext.Current.CommitAll();
					// refresh the page to ensure that the change shows up in the
					// datagrid
					Response.Redirect(HttpContext.Current.Request.Url.ToString());
					}
					catch(Exception ex)
					{
					CmsHttpContext.Current.RollbackAll();
					// after a rollback the CMS context needs to be disposed.
					CmsHttpContext.Current.Dispose();
					lblErrorMessage.Text = ex.Message;
					}
}

Save and build the solution. Let’s test it to see if it works:

1. 1. With the properties page open, click the Refresh button.

2. 2. Enter TropicalGreen—Live the Sunny Side of Life in the Description field.

3. 3. Click Update.

Look at the grid again. The description property of the TropicalGreen channel has been updated!

You must be in Update mode for the code to work correctly. Otherwise, an error occurs with the message:

Invalid mode for update. The requested action modifies the state of an object and can only be performed when the session is in the ‘Update’ mode.

The Properties dialog is already in Update mode because we have generated the URL for the Properties.aspx page to be opened in Update mode using our helper function, PrepareUrl(), earlier.