References and Using
Do:
Take care when defining references
References must be one way (or circular dependency error)
Take advantage of the using directive
Avoid:
Excessive use of the using static directive
Object vs. Class
Object:
Represents one special thing (Example:Hammer or Saw)
Defines one thing created from that template
Created at runtime with the new keyword
Class:
Represens things of the same type (Example:Product)
Define the template specifying the data and processing associated with all things of that type
Created at develop time with code
Static class doesn't create object
Object initialization
3 Ways to initialize object:
1.Setting properties
Easy to debug
When populating from database values
When modifying properties
2.Parameterized constructor
When setting the basic set of properties
3.Object initializers
When readability is important
When initializing a subset or superset of properties
Instantiating Related Objects
Usage Scenarios
One method, Always, Sometimes
One method
Initialize in the method that needs it
public string SayHello()
{
var vendor = new Vendor();
var vendorGreeting = vendor.SayHello();
}
Always
Define a property
private Vendor productVendor;
public Vendor ProductVendor
{
get { return productVendor; }
set { productVendor = value; }
}
public Product()
{
this.ProductVendor = new Vendor();
}
Sometimes
Define a property
Initialize in the property setter
"Lazy Loading"
private Vendor productVendor;
public Vendor ProductVendor
{
get
{
if (productVendor = null)
{
productVendor = new Vendor();
}
return productVendor;
}
set { productVendor = value; }
}
Null Checking
if (currentProduct != null && currentProduct.ProductVendor != null)
{
var companyName = currentProduct.ProductVendor.CompanyName;
}
C# 6 New Features
var companyName = currentProduct?.ProductVendor?.CompanyName;
"If null then null,it not then dot."
FAQ
1.What's the difference between an object and a class?
A class is a template that specifies the data and operations for an entity.
An object is an instance of that class created at runtime using the new keyword.
2.What is lazying loading and when would you use it?
Instantiating related objects when they are needed and not before.
This often involves creating the instance in the property getter for the related object