Microsoft Chart Disappearing (not rendering)?

Sometimes my charts would show, sometimes they wouldn't. Sometimes when I refresh my page the chart disappears! I found if I set the ImageStorageMode of the chart to "UseImageLocation" it started working consistently.

<asp:Chart ID="chStats" runat="server" Palette="None" Height="500px" 
    Width="500px" ImageStorageMode="UseImageLocation" >

If you use this option, you have to make sure you define a location (that has write access) in your web.config.

<appSettings>
    <add key="ChartImageHandler" value="storage=file;timeout=20;dir=C:\TempCharts;" />
</appSettings>

More Info: MSDN: Chart.ImageStorageMode Property

Chart Control - Showing all X Axis Lines (Vertical Lines)

By default when you plot more than 9 DataPoints on a chart of certain types (such as Line, Spline, etc.) the X axis will drop its labels and the X Axis Lines will disappear with them. Let's take a look:
Chart with 9 DataPoints:

Chart with 10 DataPoints:

How do I show all the X Axis labels?

You want to set the Interval property to "1".
Here is the HTML:

   1:  <asp:Chart ID="chtExample" runat="server" Height="390px" Width="470px">

   2:      <Series>

   3:          <asp:Series ChartType="Line" Name="Series1" XValueType="Date" Color="DarkBlue" BorderWidth="3">

   4:              <Points>

   5:                  <asp:DataPoint YValues="1" AxisLabel="7/31/2010" />

   6:                  <asp:DataPoint YValues="4" AxisLabel="8/7/2010" />

   7:                  <asp:DataPoint YValues="3" AxisLabel="8/14/2010" />

   8:                  <asp:DataPoint YValues="4" AxisLabel="8/21/2010" />

   9:                  <asp:DataPoint YValues="2" AxisLabel="8/28/2010" />

  10:                  <asp:DataPoint YValues="10" AxisLabel="9/4/2010" />

  11:                  <asp:DataPoint YValues="11" AxisLabel="9/11/2010" />

  12:                  <asp:DataPoint YValues="10" AxisLabel="9/18/2010" />

  13:                  <asp:DataPoint YValues="12" AxisLabel="9/25/2010" />

  14:                  <asp:DataPoint YValues="13" AxisLabel="10/2/2010" />

  15:              </Points>

  16:          </asp:Series>

  17:      </Series>

  18:      <ChartAreas>

  19:          <asp:ChartArea Name="ChartArea1">

  20:              <AxisX Interval="1">

  21:              </AxisX>

  22:          </asp:ChartArea>

  23:      </ChartAreas>

  24:  </asp:Chart>

Line 20 is where you will see the Interval property being set. With that set your chart will now show all labels on the X Axis:

This took me a while to find. Hope it helps you out!
More Info: MSDN: Axis.Interval Property

Container.DataItemIndex - Getting GridView's Row Index

Every once in a while you need to get the index of the row in a GridView that triggered an event. You can setup the CommandArgument to store the row’s index for use in your code behind. In the GridView:

<asp:GridView ID="gridView" runat="server" DataKeyNames="myId" OnRowCommand=" gridView_RowCommand">
    <Columns>
        <asp:TemplateField ShowHeader="False">
            <ItemTemplate>
                <asp:Button ID="btnAdd" runat="server" CommandArgument='<%# Container.DataItemIndex %>'
                    CommandName="Add" Text="Add" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Referencing in the code-behind:

protected void gridView_RowCommand(object sender, GridViewCommandEventArgs e)
{
    if (e.CommandName == "Add")
    {
        int myId = (int)gridView.DataKeys[Convert.ToInt32(e.CommandArgument)].Value;
    }
}

Scrollbar on a GridView

An ASP.NET GridView control will keep expanding down the page as more data is added. What if you want to control its height though? You could using Paging. You can also add scrollbars using styles. Here is an example of how you do this:

<div style="width: 200px; height: 100px; overflow: auto">
    <asp:GridView ID="gvGrid" runat="server"/>
</div>

Reading from Isolated Storage

You learned how to write to Isolated Storage in the previous post. Here is how you read from it:

IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForAssembly();

IsolatedStorageFileStream stream = new IsolatedStorageFileStream("pref.txt", FileMode.OpenOrCreate, isf);

StreamReader sr = new StreamReader(stream);

SetWidthAndHeight(sr.ReadToEnd());

sr.Close();

Isolated Storage

Isolated Storage - A private file system managed by the .NET Framework.

Why use it?
Isolated Storage provides a safe location, regardless of user access level, to store information that can be isolated by each user on the machine to store such things as user preferences.

How do I use it?
Here's an example where I store the height and width of a window in a text file on closing.

IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForAssembly();

IsolatedStorageFileStream stream = new IsolatedStorageFileStream("pref.txt", FileMode.Create, isf);

StreamWriter sw = new StreamWriter(stream);

sw.WriteLine("Width:" + this.Width);

sw.WriteLine("Height:" + this.Height);

sw.Close();

Where did this text file actually get saved?
Well, on my machine (Vista) it went into C:\Users\[User]\AppData\Local\IsolatedStorage and then through 3 more cryptic folder names until it reached the AssemFiles folder where the "pref.txt" file showed up.

The location can change depending on the OS. See here for other OS locations.

More Info: Article: When and when not to use Isolated Storage

Reading Data from the Configuration (*.config) File

In the previous post I saved data to the config file. Here is an example of how you would read data from the config file:

if (ConfigurationManager.AppSettings["Width"] != null)
{
    this.Width = Convert.ToDouble(ConfigurationManager.AppSettings["Width"]);
}

if (ConfigurationManager.AppSettings["Height"] != null)
{
    this.Height = Convert.ToDouble(ConfigurationManager.AppSettings["Height"]);
}

More Info: MSDN: ConfigurationManager.AppSettings