Design By Contract Checks. : Trace « Development Class « C# / C Sharp
Design By Contract Checks.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
namespace ObjectBakery.Utils
{
/// <summary>
/// Design By Contract Checks.
///
/// Each method generates an exception or
/// a trace assertion statement if the contract is broken.
/// </summary>
/// <remarks>
/// This example shows how to call the Require method.
/// <code>
/// public void Test(int x)
/// {
/// try
/// {
/// Check.Require(x > 1, "x must be > 1");
/// }
/// catch (System.Exception ex)
/// {
/// Console.WriteLine(ex.ToString());
/// }
/// }
/// </code>
///
/// You can direct output to a Trace listener. For example, you could insert
/// <code>
/// Trace.Listeners.Clear();
/// Trace.Listeners.Add(new TextWriterTraceListener(Console.Out));
/// </code>
///
/// or direct output to a file or the Event Log.
///
/// (Note: For ASP.NET clients use the Listeners collection
/// of the Debug, not the Trace, object and, for a Release build, only exception-handling
/// is possible.)
/// </remarks>
///
public sealed class Check
{
#region Interface
/// <summary>
/// Precondition check - should run regardless of preprocessor directives.
/// </summary>
public static void Require(bool assertion, string message)
{
if (UseExceptions)
{
if (!assertion) throw new PreconditionException(message);
}
else
{
Trace.Assert(assertion, "Precondition: " + message);
}
}
/// <summary>
/// Precondition check - should run regardless of preprocessor directives.
/// </summary>
public static void Require(bool assertion, string message, Exception inner)
{
if (UseExceptions)
{
if (!assertion) throw new PreconditionException(message, inner);
}
else
{
Trace.Assert(assertion, "Precondition: " + message);
}
}
/// <summary>
/// Precondition check - should run regardless of preprocessor directives.
/// </summary>
public static void Require(bool assertion)
{
if (UseExceptions)
{
if (!assertion) throw new PreconditionException("Precondition failed.");
}
else
{
Trace.Assert(assertion, "Precondition failed.");
}
}
/// <summary>
/// Postcondition check.
/// </summary>
public static void Ensure(bool assertion, string message)
{
if (UseExceptions)
{
if (!assertion) throw new PostconditionException(message);
}
else
{
Trace.Assert(assertion, "Postcondition: " + message);
}
}
/// <summary>
/// Postcondition check.
/// </summary>
public static void Ensure(bool assertion, string message, Exception inner)
{
if (UseExceptions)
{
if (!assertion) throw new PostconditionException(message, inner);
}
else
{
Trace.Assert(assertion, "Postcondition: " + message);
}
}
/// <summary>
/// Postcondition check.
/// </summary>
public static void Ensure(bool assertion)
{
if (UseExceptions)
{
if (!assertion) throw new PostconditionException("Postcondition failed.");
}
else
{
Trace.Assert(assertion, "Postcondition failed.");
}
}
/// <summary>
/// Invariant check.
/// </summary>
public static void Invariant(bool assertion, string message)
{
if (UseExceptions)
{
if (!assertion) throw new InvariantException(message);
}
else
{
Trace.Assert(assertion, "Invariant: " + message);
}
}
/// <summary>
/// Invariant check.
/// </summary>
public static void Invariant(bool assertion, string message, Exception inner)
{
if (UseExceptions)
{
if (!assertion) throw new InvariantException(message, inner);
}
else
{
Trace.Assert(assertion, "Invariant: " + message);
}
}
/// <summary>
/// Invariant check.
/// </summary>
public static void Invariant(bool assertion)
{
if (UseExceptions)
{
if (!assertion) throw new InvariantException("Invariant failed.");
}
else
{
Trace.Assert(assertion, "Invariant failed.");
}
}
/// <summary>
/// Assertion check.
/// </summary>
public static void Assert(bool assertion, string message)
{
if (UseExceptions)
{
if (!assertion) throw new AssertionException(message);
}
else
{
Trace.Assert(assertion, "Assertion: " + message);
}
}
/// <summary>
/// Assertion check.
/// </summary>
public static void Assert(bool assertion, string message, Exception inner)
{
if (UseExceptions)
{
if (!assertion) throw new AssertionException(message, inner);
}
else
{
Trace.Assert(assertion, "Assertion: " + message);
}
}
/// <summary>
/// Assertion check.
/// </summary>
public static void Assert(bool assertion)
{
if (UseExceptions)
{
if (!assertion) throw new AssertionException("Assertion failed.");
}
else
{
Trace.Assert(assertion, "Assertion failed.");
}
}
/// <summary>
/// Set this if you wish to use Trace Assert statements
/// instead of exception handling.
/// (The Check class uses exception handling by default.)
/// </summary>
public static bool UseAssertions
{
get
{
return useAssertions;
}
set
{
useAssertions = value;
}
}
#endregion // Interface
#region Implementation
// No creation
private Check() { }
/// <summary>
/// Is exception handling being used?
/// </summary>
private static bool UseExceptions
{
get
{
return !useAssertions;
}
}
// Are trace assertion statements being used?
// Default is to use exception handling.
private static bool useAssertions = false;
#endregion // Implementation
} // End Check
#region Exceptions
/// <summary>
/// Exception raised when a contract is broken.
/// Catch this exception type if you wish to differentiate between
/// any DesignByContract exception and other runtime exceptions.
///
/// </summary>
public class DesignByContractException : ApplicationException
{
protected DesignByContractException() { }
protected DesignByContractException(string message) : base(message) { }
protected DesignByContractException(string message, Exception inner) : base(message, inner) { }
}
/// <summary>
/// Exception raised when a precondition fails.
/// </summary>
public class PreconditionException : DesignByContractException
{
/// <summary>
/// Precondition Exception.
/// </summary>
public PreconditionException() { }
/// <summary>
/// Precondition Exception.
/// </summary>
public PreconditionException(string message) : base(message) { }
/// <summary>
/// Precondition Exception.
/// </summary>
public PreconditionException(string message, Exception inner) : base(message, inner) { }
}
/// <summary>
/// Exception raised when a postcondition fails.
/// </summary>
public class PostconditionException : DesignByContractException
{
/// <summary>
/// Postcondition Exception.
/// </summary>
public PostconditionException() { }
/// <summary>
/// Postcondition Exception.
/// </summary>
public PostconditionException(string message) : base(message) { }
/// <summary>
/// Postcondition Exception.
/// </summary>
public PostconditionException(string message, Exception inner) : base(message, inner) { }
}
/// <summary>
/// Exception raised when an invariant fails.
/// </summary>
public class InvariantException : DesignByContractException
{
/// <summary>
/// Invariant Exception.
/// </summary>
public InvariantException() { }
/// <summary>
/// Invariant Exception.
/// </summary>
public InvariantException(string message) : base(message) { }
/// <summary>
/// Invariant Exception.
/// </summary>
public InvariantException(string message, Exception inner) : base(message, inner) { }
}
/// <summary>
/// Exception raised when an assertion fails.
/// </summary>
public class AssertionException : DesignByContractException
{
/// <summary>
/// Assertion Exception.
/// </summary>
public AssertionException() { }
/// <summary>
/// Assertion Exception.
/// </summary>
public AssertionException(string message) : base(message) { }
/// <summary>
/// Assertion Exception.
/// </summary>
public AssertionException(string message, Exception inner) : base(message, inner) { }
}
#endregion // Exception classes
}
Related examples in the same category
| 1. | Use Trace.Fail to alert a fail | ||
| 2. | Trace.WriteLine | ||
| 3. | demonstrates post-deployment tracing |  | |
| 4. | demonstrates the use of TraceListener objects |  |