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Inheritance Hierarchy for Exceptions in C#
The mapping for exceptions is based on the inheritance hierarchy shown below:
Inheritance structure for exceptions.
The ancestor of all exceptions is
System.Exception. Derived from that is
Ice.Exception, which provides the definitions of a number of constructors.
Ice.UserException are derived from
Ice.Exception and form the base of all run-time and user exceptions, respectively.
The constructors defined in
Ice.Exception have the following signatures:
Each concrete derived exception class calls these constructors. The second constructor initializes the
InnerException property of
System.Exception. (Both constructors set the
Message property to the empty string.)
ice_id method returns the Slice type id of the exception, for example "
C# Mapping for User Exceptions
Here is a fragment of the Slice definition for our world time server once more:
These exception definitions map as follows:
Each Slice exception is mapped to a C# partial class with the same name. For each exception member, the corresponding class contains a public data member. (Obviously, because
BadZoneName do not have members, the generated classes for these exceptions also do not have members.) Optional data members are mapped to instances of the
The inheritance structure of the Slice exceptions is preserved for the generated classes, so
BadZoneName inherit from
All user exceptions are derived from the base class
Ice.UserException. This allows you to catch all user exceptions generically by installing a handler for
Ice.UserException. Similarly, you can catch all Ice run-time exceptions with a handler for
Ice.LocalException, and you can catch all Ice exceptions with a handler for
All exceptions provide the usual
Equals methods, as well as the
!= comparison operators.
The generated exception classes also contain other methods that are not shown here; these methods are internal to the C# mapping and are not meant to be called by application code.
C# Default Constructors for User Exceptions
An exception has a default constructor that initializes data members as follows:
|Data Member Type||Default Value|
The constructor won't explicitly initialize a data member if the default C# behavior for that type produces the desired results.
If you wish to ensure that data members of primitive and enumerated types are initialized to specific values, you can declare default values in your Slice definition. The default constructor initializes each of these data members to its declared value instead.
An exception also provides a constructor that accepts one parameter for each data member so that you can construct and initialize a class instance in a single statement (instead of first having to construct the instance and then assign to its members). For a derived exception, this constructor accepts one argument for each base exception member, plus one argument for each derived exception member, in base-to-derived order. For each optional data member, the constructor accepts an
Ice.Optional parameter of the appropriate type.
C# Mapping for Run-Time Exceptions
The Ice run time throws run-time exceptions for a number of pre-defined error conditions. All run-time exceptions directly or indirectly derive from
Ice.LocalException (which, in turn, derives from
Ice.LocalException implements a
Clone method that is inherited by its derived exceptions, so you can make memberwise shallow copies of exceptions.
By catching exceptions at the appropriate point in the inheritance hierarchy, you can handle exceptions according to the category of error they indicate:
This is the root of the inheritance tree for both run-time and user exceptions.
This is the root of the inheritance tree for run-time exceptions.
This is the root of the inheritance tree for user exceptions.
This is the base exception for both operation-invocation and connection-establishment timeouts.
This exception is raised when the initial attempt to establish a connection to a server times out.
For example, a
ConnectTimeoutException can be handled as
You will probably have little need to catch run-time exceptions as their most-derived type and instead catch them as
LocalException; the fine-grained error handling offered by the remainder of the hierarchy is of interest mainly in the implementation of the Ice run time. Exceptions to this rule are the exceptions related to facet and object life cycles, which you may want to catch explicitly. These exceptions are
- User Exceptions
- Run-Time Exceptions
- C-Sharp Mapping for Identifiers
- C-Sharp Mapping for Modules
- C-Sharp Mapping for Built-In Types
- C-Sharp Mapping for Enumerations
- C-Sharp Mapping for Structures
- C-Sharp Mapping for Sequences
- C-Sharp Mapping for Dictionaries
- C-Sharp Collection Comparison
- C-Sharp Mapping for Constants
- C-Sharp Mapping for Optional Values
- Object Life Cycle