19. What are lambda expressions in LINQ?
A lambda expression is a function without a name that calculates and returns a single value. All lambda expressions use the lambda operator =>, which read as goes to. The left side of the lambda operator specifies the input parameters and the right side holds the expression or statement block.
20. Before you query a DataSet object by using LINQ to DataSet, you must first populate the dataset How can you do this?
You can load the data into the dataset by using different methods, such as:
- Using the DataAdapter class
- Using LINQ to SQL
21. What are the different implementations of LINQ?
The different implementations of LINQ are:
- LINQ to SQL – Refers to a component of.NET Framework version 3.5 that provides a run-time infrastructure to manage relational data as objects.
- LINQ to DataSet – Refers to a component that makes it easier and faster to query over data cached in a DataSet object.
- LINQ to XML – Provides an in-memory XML programming interface.
- LINQ to Objects – Refers to the use of LINQ queries with any IEnumerable or IEnumerable(T)collection directly, without the use of an intermediate LINQ provider or API, such as LINQ to SQL or LINQ to XML.
22. Which command-line tool generates code and mapping for the LINQ to SQL component of .NET Framework?
The SqlMetal.exe command-line tool generates code and map the LINQ to SQL component.
23. Name the control that exposes the LINQ features to Web developers through the ASP.NET data-source control architecture.
The LinqDataSource control exposes the LINQ features to Web developers through the ASP.NET data-source control architecture.
24. What is the difference between the Select clause and SelectMany() method in LINQ?
Both the Select clause and SelectMany() method are used to produce a result value from a source of values. The difference lies in the result set. The Select clause is used to produce one result value for every source value. The result value is a collection that has the same number of elements from the query. In contrast, theSelectMany() method produces a single result that contains a concatenated collection from the query.