Dataset and Diffgram in Ado.Net

Question

What is Dataset and Diffgram in Ado.net.

Satyapriya Nayak · Answer

Hi Sharad The Role of DataSets in ADO.NET The important of datasets can never be denied nor it can be questioned. DataSet is a mirror image of the table or the query which you run. DataSets makes it easier to edit and update the information. Another good thing is that datasets are disconnected in nature so if you make any changes in the dataset it will not reflect in the database unless use special methods to perform the change and confirm it. Using DataSets in ASP.NET Let's see how we can use datasets in Asp.net. The most common way of using the DataSet control is with the dataadapter. The DataAdapter fills the dataset control with data coming from the database. Let's see how we can perform this simple action: SqlDataAdapter ad = new SqlDataAdapter(SELECT * FROm CategoriesmyConnection); DataSet ds = new DataSet(); ad.Fill(dsCategories); DataGrid1.DataSource = ds; DataGrid1.DataBind(); Explanation of the code: 1. First we declare a simple dataadapter instance which fetches all the rows from the Categories table. ( Categories table is present in the Northwind database which is shipped with Sql Server 2000 ). 2. New we created an instance of the DataSet control. 3. Next we fill the dataset with the data coming from the dataadapter control. As you can see that I have written ad.Fill(dsCategories); you can also write ad.Fill(ds); and this will work fine too. In the former case I was telling the dataadapter which table I am using in my query and later the dataadapter was finding the table itself. 4. Finally I used DataGrid to bind the data on the screen. Iterating through the DataSet: Here is a simple code to iterate through the dataset and select individual items instead of selecting all the data in the DataSet. SqlDataAdapter ad = new SqlDataAdapter(SELECT * FROm CategoriesmyConnection); DataSet ds = new DataSet(); ad.Fill(dsCategories); DataTable dt = ds.Tables[Categories]; Response.Write(dt.Rows[0][1].ToString()) ; 1) First few lines are identical which we have done before. 2) In the forth line we declared the DataTable object. DataTable object is used to hold a single table. As I already told you that dataset can hold multiple tables depending upon the query so we can assign a single table from the dataset to the datatable object. I have done that using the line. DataTable dt = ds.Tables[Categories]; 3) Next we are printing the first row of the second column. Always remember that the number of the rows and columns in the database does not start with 1 but it starts at 0. So in this line of code: Response.Write(dt.Rows[0][1].ToString()) ; This line of code means that get Row '0' and Column 1 of the from the datatable. And so we get the value and it prints out Beverages. Saving dataSets in Session State: DataSets can also be saved in the Session State so that it can be available in other areas of the application and in new pages. The way of storing the DataSet in Session State is very easy. Session[MyDataSet] = DataSet; Later if you want to retrieve the DataSet from the Session State you can easily do this by using this line of code: DataSet ds = (DataSet) Session[MyDataSet] As you can see that when I am retrieving the values from the Session object I am casting it into the dataset object. This is because this is explicit conversion and requires casting. I am unboxing in this case. Please refer the below links http://www.exforsys.com/tutorials/asp.net/managing-data-with-ado.net-datasets-and-csharp.html http://dhananjayspeaks.wordpress.com/2012/01/23/introduction-to-dataset-in-ado-net/ Thanks

RanjithKumar chiguruvada · Answer

Hi gupta ADO.NET introduced the DataSet class to support the disconnected distributed data- access scenarios.With DataSet the data retrieved from the database is cached in- memory in addition to the constraints and relationships among the tables. When the ADO.NET DataSet is serialized as XML (for example when returning a DataSet from an ASP.NET XML Web service method)the XML format used for DataSet serialization is known as DiffGram. A DiffGram is an XML format that identifies current and original versions of data elements.The DataSet uses the DiffGram format to load and persist its contents and to serialize its contents for transport across a network connection. When a DataSet is written as a DiffGram it populates the DiffGram with all the necessary information to accurately recreate the contents though not the schema of the DataSet including column values from both the Original and Current row versions row error information and row order. When sending and retrieving a DataSet from an XML Web service the DiffGram format is implicitly used. Additionally when loading the contents of a DataSet from XML using the ReadXml method or when writing the contents of a DataSet in XML using the WriteXml method you can select that the contents be read or written as a DiffGram. For more information see Loading a DataSet from XML and Writing a DataSet as XML Data. While the DiffGram format is primarily used by the .NET Framework as a serialization format for the contents of a DataSetyou can also use DiffGrams to modify data in tables in a Microsoft SQL Server database.