Initialize the web cam

private CaptureSource _captureSource;
private VideoBrush _videoBrush;
private ImageBrush _imageBrush;

_captureSource = new CaptureSource();
_captureSource.CaptureImageCompleted += (o, e) =>
{
    _imageBrush = new ImageBrush();
    _imageBrush.ImageSource = e.Result;
    rectWebCamView.Fill = _imageBrush;
};
_captureSource.CaptureFailed += (o, e) =>
{
    MessageBox.Show(e.ErrorException.Message);
};

Start the web cam, the rectWebCamView is a Rectangle.

if (_captureSource.State != CaptureState.Started)
{
    _captureSource.VideoCaptureDevice =
        CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();
    _videoBrush = new VideoBrush();
    _videoBrush.SetSource(_captureSource);
    rectWebCamView.Fill = _videoBrush;

    if (CaptureDeviceConfiguration.RequestDeviceAccess())
    {
        _captureSource.Start();
    }
}

The RequestDeviceAccess() method invokes a request dialog for accessing the webcame like this.

Request Access dialog

Note: The RequestAccess must be called in response to a user initiated event, such as a Button Click event.

Stop the web cam

_captureSource.Stop();

And finally the capture image.

if (_captureSource.State == CaptureState.Started)
{
    _captureSource.CaptureImageAsync();
}

The method will invoke CaptureImageCompleted event, and which will capture the image and display it in the rectangle. The XAML code contains only 3 buttons and one rectangle, so I am not posting the XAML code.

Happy programming

There is a duplicate 'system.web.extensions/ scripting/ scriptResourceHandler' section defined.

But after verifying the web.config file, I couldn’t find the duplicate entry. After searching I found that this issue is with ASP.NET 4.0 / VS 2010. The workaround for the scenario is to delete or comment out all the system.web.extensions configuration section definitions and configuration section group definitions from the application-level web.config file. Because all these settings are available in the top application level web.config file, will be under the configSections element.

Here is my sample Database design and which contains few of my blog posts.

Database Structure

And here is the implementation using generic ashx handler, which helps to create RSS feeds. Following snippet will read all the values from the table and creating list of SyndicationItem using SqlDataReader.

using (SqlCommand command = new SqlCommand("SELECT * FROM tblPosts", connection))
{
    SqlDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection);
    while (reader.Read())
    {
        feedList.Add(new SyndicationItem(
            reader["PostTitle"].ToString(),
            reader["PostContent"].ToString(),
            new Uri(string.Format(APP_URL,
                reader["PostId"].ToString())),
            reader["PostId"].ToString(),
            DateTimeOffset.Parse(reader["PostDate"].ToString())));
    }
}

And next snippet creating a SyndicationFeed which will help to create RSS using SyndicationItems. Based on the querystring, it is generating either ATOM or RSS feed.

SyndicationFeed feeds =
    new SyndicationFeed("DOTNETTHOUGHTS",
        "A DOTNET DEVELOPER'S TECHNICAL BLOG",
        new Uri("http://dotnetthoughts.net/feed"), feedList);
feeds.Copyright =
    new TextSyndicationContent("Copyright (C) 2011 dotnetthoughts.net");
feeds.Authors.Add(
    new SyndicationPerson("anuraj@dotnetthoughts.net", "Anuraj", "dotnetthoughts.net"));
feeds.Language = "en-us";
string responseString;
using (var ms = new MemoryStream())
{
    using (XmlWriter xmlWriter = XmlWriter.Create(ms))
    {
        string rss = HttpContext.Current.Request.QueryString["rss"];
        if (string.IsNullOrWhiteSpace(rss))
        {
            feeds.SaveAsAtom10(xmlWriter);
        }
        else
        {
            feeds.SaveAsRss20(xmlWriter);
        }
        xmlWriter.Flush();
        xmlWriter.Close();
    }
    responseString = System.Text.ASCIIEncoding.UTF8.GetString(ms.ToArray());
}

context.Response.ContentType = "text/xml";
context.Response.Write(responseString);
context.Response.End();

And here is the screenshot of RSS feed in Internet Explorer.

RSS Feed in Internet Explorer

There are more useful tags which you can use to create the RSS feed, such as the category or an unique ID. You found more information on Creating RSS Feed in the RSS 2.0 specification page.

Happy Programming.

I created a web page with a Gridview with Paging enabled. First column of the grid view is Template Column which contains the Checkbox for selection of rows. And the state information is saved while paging, and retrived on Prerender event of the GridView. And here is the implementation.

ASPX Markup

<asp:GridView runat="server" ID="gvSample" AutoGenerateColumns="false" AllowPaging="True"
            OnPageIndexChanging="gvSample_PageIndexChanging" OnPreRender="gvSample_PreRender">
            <Columns>
                <asp:TemplateField>
                    <ItemTemplate>
                        <asp:CheckBox runat="server" ID="chkSelected" />
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:BoundField DataField="Name" HeaderText="Name" />
                <asp:BoundField DataField="Email" HeaderText="Email" />
            </Columns>
            <PagerSettings PageButtonCount="10" />
        </asp:GridView>

And here is the code-behind for it

protected void gvSample_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    string pageId = string.Format("Page{0}", gvSample.PageIndex);
    bool[] selectedCheckboxes = new bool[gvSample.PageSize];
    for (int i = 0; i < gvSample.Rows.Count; i++)
    {
        TableCell cell = gvSample.Rows[i].Cells[0];
        selectedCheckboxes[i] = (cell.FindControl("chkSelected") as CheckBox).Checked;
    }

    ViewState[pageId] = selectedCheckboxes;
    gvSample.PageIndex = e.NewPageIndex;
    //Bind the gridview again
}

protected void gvSample_PreRender(object sender, EventArgs e)
{
    string pageId = string.Format("Page{0}", gvSample.PageIndex);
    bool[] selectedCheckboxes = ViewState[pageId] as bool[];
    if (selectedCheckboxes != null)
    {
        for (int i = 0; i < gvSample.Rows.Count; i++)
        {
            TableCell cell = gvSample.Rows[i].Cells[0];
            (cell.FindControl("chkSelected") as CheckBox).Checked = selectedCheckboxes[i];
        }
    }
}

Welcome for Feedbacks/Suggestions/Comments. Thank you for reading my blog. Happy Programming

for (var i = 0; i < 10; i++)
{
	var row = dataTable.NewRow();
	row[0] = i.ToString();
	dataTable.Rows.Add(row);
}

for (int i = 0; i < 10; i++)
{
	var dr = dataTable.Rows[i];
	dr[0] = (i + 10).ToString();
	//This line throws exception
	dataTable1.Rows.Add(dr);
}

He was getting an exception like “This row already belongs to another table”. This exception is coming because of A DataRow can only belong to a single data table.

ArgumentException – This row already belongs to another table

I got this exception many times (in good(?) old ASP.Net 1.1 days ) and able to fix, but today I couldn’t remember the solution. Later we fixed it, and here is the solutions.

1. Using Item array property : Instead of using the row directly from other second table, use the ItemArray property.

   var dr = dataTable.Rows[i].ItemArray;
   dr[0] = (i + 10).ToString();
   dataTable.Rows.Add(dr);
   

2. Using DataTable.Clone() and ImportRow() methods : Instead of using creating a new DataTable with same schema again, clone the DataTable and using ImportRow method.

   DataTable dataTable1 = dataTable.Clone();
   var dr = dataTable.Rows[i];
   dr[0] = (i + 10).ToString();
   dataTable1.ImportRow(dr);
   

Happy coding and Thanks to Sarath