Interface Properties in Visual C#

Creation QR Code ISO/IEC18004 in Visual C# Interface Properties

Like methods, properties are specified in an interface without any body Here is the general form of a property specification: // interface property type name { get; set; }

12:

Of course, only get or set will be present for read-only or write-only properties, respectively Although the declaration of a property in an interface looks similar to how an autoimplemented property is declared in a class, the two are not the same The interface declaration does not cause the property to be auto-implemented It only specifies the name and type of the property Implementation is left to each implementing class Also, no access modifiers are allowed on the accessors when a property is declared in an interface Thus, the set accessor, for example, cannot be specified as private in an interface Here is a rewrite of the ISeries interface and the ByTwos class that uses a property called Next to obtain and set the next element in the series:

// Use a property in an interface using System; public interface ISeries { // An interface property int Next { get; // return the next number in series set; // set next number } } // Implement ISeries class ByTwos : ISeries { int val; public ByTwos() { val = 0; } // Get or set value public int Next { get { val += 2; return val; } set { val = value; } } } // Demonstrate an interface property class SeriesDemo3 { static void Main() { ByTwos ob = new ByTwos(); // Access series through a property for(int i=0; i < 5; i++) ConsoleWriteLine("Next value is " + obNext); ConsoleWriteLine("\nStarting at 21"); obNext = 21;

Part I:

for(int i=0; i < 5; i++) ConsoleWriteLine("Next value is " + obNext); } }

The output from this program is shown here:

Starting at 21 Next value is 23 Next value is 25 Next value is 27 Next value is 29 Next value is 31

An interface can specify an indexer A one-dimensional indexer declared in an interface has this general form: // interface indexer element-type this[int index] { get; set; } As before, only get or set will be present for read-only or write-only indexers, respectively Also, no access modifiers are allowed on the accessors when an indexer is declared in an interface Here is another version of ISeries that adds a read-only indexer that returns the i-th element in the series

// Add an indexer in an interface using System; public interface ISeries { // An interface property int Next { get; // return the next number in series set; // set next number } // An interface indexer int this[int index] { get; // return the specified number in series } }

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// Implement ISeries class ByTwos : ISeries { int val;

public ByTwos() { val = 0; } // Get or set value using a property public int Next { get { val += 2; return val; } set { val = value; } } // Get a value using an index public int this[int index] { get { val = 0; for(int i=0; i < index; i++) val += 2; return val; } } } // Demonstrate an interface indexer class SeriesDemo4 { static void Main() { ByTwos ob = new ByTwos(); // Access series through a property for(int i=0; i < 5; i++) ConsoleWriteLine("Next value is " + obNext); ConsoleWriteLine("\nStarting at 21"); obNext = 21; for(int i=0; i < 5; i++) ConsoleWriteLine("Next value is " + obNext); ConsoleWriteLine("\nResetting to 0"); obNext = 0; // Access series through an indexer for(int i=0; i < 5; i++) ConsoleWriteLine("Next value is " + ob[i]); } }

Part I:

The output from this program is shown here:

Starting at 21 Next value is 23 Next value is 25 Next value is 27 Next value is 29 Next value is 31 Resetting to 0 Next value is 0 Next value is 2 Next value is 4 Next value is 6 Next value is 8