Cómo: Utilizar excepciones específicas en un bloque CatchHow to use specific exceptions in a catch block

En general, en programación es recomendable detectar un tipo de excepción específico en lugar de usar una instrucción catch básica.In general, it's good programming practice to catch a specific type of exception rather than use a basic catch statement.

Cuando se produce una excepción, se pasa a la pila y cada bloque Catch tiene la oportunidad de controlarla.When an exception occurs, it is passed up the stack and each catch block is given the opportunity to handle it. El orden de las instrucciones Catch es importante.The order of catch statements is important. Ponga los bloques Catch dirigidos a excepciones específicas antes de un bloque Catch de excepción general o el compilador podría emitir un error.Put catch blocks targeted to specific exceptions before a general exception catch block or the compiler might issue an error. El bloque Catch adecuado se determina haciendo coincidir el tipo de la excepción con el nombre de la excepción especificada en el bloque Catch.The proper catch block is determined by matching the type of the exception to the name of the exception specified in the catch block. Si no hay ningún bloque Catch específico, la excepción se detecta mediante un bloque Catch general, si existe alguno.If there is no specific catch block, the exception is caught by a general catch block, if one exists.

En el siguiente ejemplo de código se usa un bloque try/catch para detectar una InvalidCastException.The following code example uses a try/catch block to catch an InvalidCastException. El ejemplo crea una clase denominada Employee con una propiedad única, el nivel de empleado (Emlevel).The sample creates a class called Employee with a single property, employee level (Emlevel). Un método, PromoteEmployee, toma un objeto e incrementa el nivel del empleado.A method, PromoteEmployee, takes an object and increments the employee level. Una InvalidCastException se produce cuando una instancia de DateTime se pasa al método PromoteEmployee.An InvalidCastException occurs when a DateTime instance is passed to the PromoteEmployee method.

using namespace System;

public ref class Employee
{
public:
    Employee()
    {
        emlevel = 0;
    }

    //Create employee level property.
    property int Emlevel
    {
        int get()
        {
            return emlevel;
        }
        void set(int value)
        {
            emlevel = value;
        }
    }

private:
    int emlevel;
};

public ref class Ex13
{
public:
    static void PromoteEmployee(Object^ emp)
    {
        //Cast object to Employee.
        Employee^ e = (Employee^) emp;
        // Increment employee level.
        e->Emlevel++;
    }

    static void Main()
    {
        try
        {
            Object^ o = gcnew Employee();
            DateTime^ newyears = gcnew DateTime(2001, 1, 1);
            //Promote the new employee.
            PromoteEmployee(o);
            //Promote DateTime; results in InvalidCastException as newyears is not an employee instance.
            PromoteEmployee(newyears);
        }
        catch (InvalidCastException^ e)
        {
            Console::WriteLine("Error passing data to PromoteEmployee method. " + e->Message);
        }
    }
};

int main()
{
    Ex13::Main();
}
using System;

public class Employee
{
    //Create employee level property.
    public int Emlevel
    {
        get
        {
            return(emlevel);
        }
        set
        {
            emlevel = value;
        }
    }

    private int emlevel = 0;
}

public class Ex13
{
    public static void PromoteEmployee(Object emp)
    {
        // Cast object to Employee.
        var e = (Employee) emp;
        // Increment employee level.
        e.Emlevel = e.Emlevel + 1;
    }

    public static void Main()
    {
        try
        {
            Object o = new Employee();
            DateTime newYears = new DateTime(2001, 1, 1);
            // Promote the new employee.
            PromoteEmployee(o);
            // Promote DateTime; results in InvalidCastException as newYears is not an employee instance.
            PromoteEmployee(newYears);
        }
        catch (InvalidCastException e)
        {
            Console.WriteLine("Error passing data to PromoteEmployee method. " + e.Message);
        }
    }
}
Public Class Employee
    'Create employee level property.
    Public Property Emlevel As Integer
        Get
            Return emlevelValue
        End Get
        Set
            emlevelValue = Value
        End Set
    End Property

    Private emlevelValue As Integer = 0
End Class

Public Class Ex13
    Public Shared Sub PromoteEmployee(emp As Object)
        ' Cast object to Employee.
        Dim e As Employee = CType(emp, Employee)
        ' Increment employee level.
        e.Emlevel = e.Emlevel + 1
    End Sub

    Public Shared Sub Main()
        Try
            Dim o As Object = New Employee()
            Dim newYears As New DateTime(2001, 1, 1)
            ' Promote the new employee.
            PromoteEmployee(o)
            ' Promote DateTime; results in InvalidCastException as newYears is not an employee instance.
            PromoteEmployee(newYears)
        Catch e As InvalidCastException
            Console.WriteLine("Error passing data to PromoteEmployee method. " + e.Message)
        End Try
    End Sub
End Class

Vea tambiénSee also