I define an interface and a class like this:
interface ITextBox
{
double Left { get; set; }
}
class TimeTextBox : ITextBox
{
public TimeTextBox(ITextBox d)
{
Left = d.Left;
}
public double Left { get; set; }
}
I want to create an instance of this class like this:
ITextBox s;
s.Left = 12;
TimeTextBox T = new TimeTextBox(s);
But this error occure:
Use of unassigned local variable 's'
You haven't instantiated s before trying to use it.
You need to do something like this:
ITextBox s = new SomeClassThatImplementsITextBox();
TimeTextBox t = new TimeTextBox(s);
An interface is just a contract. It only defines structure. You have to have a concrete implementation of a class that implements that interface.
Quoted from: http://msdn.microsoft.com/en-us/library/87d83y5b(v=vs.110).aspx
"An interface contains only the signatures of methods, properties, events or indexers. A class or struct that implements the interface must implement the members of the interface that are specified in the interface definition."
You need a class or struct to implement your interface, and that class or struct needs to be instantiated into an object, then passed into your constructor.
Implementation:
class Example : ITextBox
{
public double Left { get; set; }
}
Instantiation:
Example s = new Example();
ITextBox s; just defines a reference to something that implements ITextBox. It does not define an instance. So on line 2 when you set a property on it the object doesn't exist. The compiler prevents you from making this mistake which is why you get a compiler error.
You need to do ITextBox s = new MyClassThatImplementsITextBox();
