Wednesday, September 23, 2015

Caching application data in

Suggested Videos
Part 123 - Web form caching based on GET and POST requests
Part 124 - Caching multiple versions of user control using VaryByControl
Part 125 - Caching multiple versions of user control using VaryByParam

In parts 119 to 125 of the video tutorial, we discussed about
1. Caching webforms
2. Caching multiple responses of webforms
3. Fragment caching using user controls
4. Caching multiple versions of usercontrols

Please watch these videos, from the video tutorial by clicking here, before proceeding.

In this video we will discuss about caching application data. It is possible to store application data in the web server memory, using the CACHE object, so that the data can be retrieved faster. For example, let us say, we have a stored procedure that takes 5 seconds to execute and return data. We can cache the data returned by this stored procedure with in an web application using the CACHE object, so that, next time when we try to access the data, we can get it from the cache, rather than reprocessing the stored procedure again.

We will be using "tblProducts" table for this demo. If you need the script to create and populate this table, please refer to Part 122

The following stored procedure takes 5 seconds to execute and return data. We are using WAITFOR DELAY, to introduce artificial query processing time of 5 seconds. 
CREATE Procedure spGetProducts  
 Waitfor Delay '00:00:05'  
 Select * from tblProducts  

Create an web application, copy and paste the following HTML in WebForm1.aspx.
<div style="font-family:Arial">
    <asp:Button ID="btnGetProducts" runat="server" Text="Get Products Data" 
        onclick="btnGetProducts_Click" />
    <br /><br />
    <asp:GridView ID="gvProducts" runat="server">
    <br />
    <asp:Label ID="lblMessage" Font-Bold="true" runat="server"></asp:Label>

Copy and paste the following code in WebForm1.aspx.cs. The code is well documented and is self explanatory.
protected void btnGetProducts_Click(object sender, EventArgs e)
    DateTime dtStartDateTime = DateTime.Now;
    System.Text.StringBuilder sbMessage = new System.Text.StringBuilder();
    // Check if the data is already cached
    if (Cache["ProductsData"] != null)
        // If data is cached, retrieve data from Cache using the key "ProductsData"
        DataSet ds = (DataSet)Cache["ProductsData"];
        // Set the dataset as the datasource
        gvProducts.DataSource = ds;
        // Retrieve the total rows count
        sbMessage.Append(ds.Tables[0].Rows.Count.ToString() + " rows retrieved from cache.");
    // If the data is not cached
        // Get the data from the database
        DataSet ds = GetProductsData();
        // Cache the dataset using the key "ProductsData"
        Cache["ProductsData"] = ds;
        // Set the dataset as the datasource
        gvProducts.DataSource = ds;
        sbMessage.Append(ds.Tables[0].Rows.Count.ToString() + " rows retrieved from database.");
    DateTime dtEndDateTime = DateTime.Now;
    sbMessage.Append((dtEndDateTime - dtStartDateTime).Seconds.ToString() + " Seconds Load Time");
    lblMessage.Text = sbMessage.ToString();

private DataSet GetProductsData()
    string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
    SqlConnection con = new SqlConnection(CS);
    SqlDataAdapter da = new SqlDataAdapter("spGetProducts", con);
    da.SelectCommand.CommandType = CommandType.StoredProcedure;

    DataSet dsProducts = new DataSet();

    return dsProducts;

In this video, we discussed about storing application data in cache, using direct assignment. That is using a key and assiging value to it, as shown below.
Cache["ProductsData"] = ds

In our next video, we will discuss about all the other options that are available, to store data in the Cache object.

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