Ado Dot Net Interview Questions And Answers

Question 28: Explain the properties and methods of Command Object.

Answer: The command object is one of the basic components of ADO .NET.

  • The Command Object uses the connection object to execute SQL queries.
  • The queries can be in the form of Inline text, Stored Procedures or direct Table access.
  • An important feature of Command object is that it can be used to execute queries and Stored Procedures with Parameters.
  • If a select query is issued, the result set it returns is usually stored in either a DataSet or a DataReader object.
  • Associated Properties of SqlCommand class

    Property Type of Access Description
    Connection Read/Write The SqlConnection object that is used by the command object to execute SQL queries or Stored Procedure.
    CommandText Read/Write Represents the T-SQL Statement or the name of the Stored Procedure.
    CommandType Read/Write This property indicates how the CommandText property should be interpreted. The possible values are: 1. Text (T-SQL Statement) 2. StoredProcedure (Stored Procedure Name) 3. TableDirect
    CommandTimeout Read/Write This property indicates the time to wait when executing a particular command. Default Time for Execution of Command is 30 Seconds. The Command is aborted after it times out and an exception is thrown.

    Now, let us have a look at various execute methods that can be called from a Command Object.

    Property Description
    ExecuteNonQuery This method executes the command specifies and returns the number of rows affected.
    ExecuteReader The ExecuteReader method executes the command specified and returns an instance of instance of SqlDataReader class.
    ExecuteScalar This method executes the command specified and returns the first column of first row of the result set. The remaining rows and column are ignored
    ExecuteXMLReader This method executes the command specified and returns an instance of XmlReader class. This method can be used to return the result set in the form of an XML document

    See for more detail:

    Question 15: Describe the DataView in ADO.NET?

    Answer: A DataView enables you to create different views of the data stored in a DataTable, a capability that is often used in data binding applications. Using a DataView, you can expose the data in a table with different sort orders, and you can filter the data by row state or based on a filter expression. A DataView provides a dynamic view of data whose content, ordering, and membership reflect changes to the underlying DataTable as they occur. This is different from the Select method of the DataTable, which returns a DataRow array from a table per particular filter and/or sort order and whose content reflects changes to the underlying table, but whose membership and ordering remain static. The dynamic capabilities of the DataView make it ideal for data-binding applications.

    How we can create a DataView

    There are two ways to create a DataView. You can use the DataView constructor, or you can create a reference to the DefaultView property of the DataTable. The DataView constructor can be empty, or will also take either a DataTable as a single argument, or a DataTable along with filter criteria, sort criteria, and a row state filter.

    See for more detail:

    2 What is the difference between Dataset.clone and Dataset.copy?

  • Dataset.clone object copies structure of the dataset, including relations, schemas, and constraints. This does not copy data in the table.
  • Dataset.copy – Copies both data and structure from the table.
  • ADO.NET Interview Questions and Answers

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