Multilevel subreports in SSRS Reporting Services

CODE SNIPPETS, TUTORIAL

Microsoft's SSRS Reporting services allows 20 levels of subreports. A Subreport can be helpful when data from different datasets need to be embedded within lists, tables or matrix. When using business objects from memory, tables and lists do not allow inputting fields from different datasets. For eg: if a List is linked to a class Product, and you would like to embed a table within this list from a different class, SSRS won't let you do it. This is where subreports can be useful.

For this tutorial, I will create a main report and 2 levels of subreports.

1. Create the main report MainReport.rdlc.
2. Create two additional reports SubReport1.rdlc and SubReport2.rdlc
3. In MainReport.rdlc, drag and place a Subreport placeholder from the toolbox. Right click to view the properties and under "Use this report as a subreport" textbox, write SubReport1. Note that the extension ".rdlc" is not written in this textbox
4. Repeat step 3 in SubReport1 to create a second-level subreport
5. Now we need to bind datasources and provide data to the subreports.
6. Open Form.cs. Write the following lines in the Form1_Load() method before the this.reportViewer1.RefreshReport();

               
          reportViewer1.LocalReport.SubreportProcessing +=
new SubreportProcessingEventHandler(LocalReport_SubreportProcessing);
7. Now create a handler for the above method:

private void LocalReport_SubreportProcessing(object sender, SubreportProcessingEventArgs e){

//this should match the DataSet name given in .rdlc filee.DataSources.Add(new ReportDataSource("Grade", (this.bindingSource6)));e.DataSources.Add(
new ReportDataSource("Measurement", (this.bindingSource5)));}

Make sure the dataset name("Grade") matches the name given in .rdlc file.

8. Go to Form's designer and click on smartag. Choose Report1.rdlc to make this the main report.

When to use Inheritance, Composition, Interface, Aggregation

Composition

To identify composition associations, look for classes that cannot exist without other classes. Look for "wholes" and "parts". Ask, "Is this class part of another class?". The key question to ask is - Is this class destroyed when another class is destroyed?

Aggregation

The key difference between an aggregation and a composition is, in an aggregation, the part is not destroyed when the whole is destroyed. The part may be independent of the whole but the whole requires the part. For eg: A car class would require an engine class, chassis class. To identify aggregation, ask - Is this class part of another class and is it independent of the other class?

Inheritance

Inheritance provides the mechanism for new classes to be formed from the attributes and behavior of exisitng classes. Inheritance is best suited for relatively shallow class hierarchies. Use Inheritnace when:

• The inheritance hieracrchy represents an is-a relaltionship and not a has-a(composition/aggregation) relationship.
• The same behavior is applied to different data typoes.
• The class hierarchy is reasonably shallow, and unlikely to become much deeper over time.

Interface

Like an inherited classm an interface provides a common specification for behavior, but, uunlike an inherited class, an interface cannot be created. The behavior has been abstracted out my any particular class and specifically implemented by all classes that need it.  Use interface inheritance when:

• Unrelated object types need to provide the same behavior
• Multiple inheritance is needed.
• Inheritance is prohibited. For example C# structures cannot inherit from classes, but can implement interfaces.