本文整理汇总了VB.NET中System.Reflection.Emit.ILGenerator.BeginExceptionBlock方法的典型用法代码示例。如果您正苦于以下问题:VB.NET ILGenerator.BeginExceptionBlock方法的具体用法?VB.NET ILGenerator.BeginExceptionBlock怎么用?VB.NET ILGenerator.BeginExceptionBlock使用的例子?那么, 这里精选的方法代码示例或许可以为您提供帮助。
在下文中一共展示了ILGenerator.BeginExceptionBlock方法的1个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的VB.NET代码示例。
示例1: ILThrowExceptionDemo
' 导入命名空间
Imports System.Reflection
Imports System.Reflection.Emit
Class ILThrowExceptionDemo
Public Shared Sub Main()
Dim current As AppDomain = AppDomain.CurrentDomain
Dim myAsmName As New AssemblyName()
myAsmName.Name = "AdderExceptionAsm"
Dim myAsmBldr As AssemblyBuilder = _
current.DefineDynamicAssembly(myAsmName, _
AssemblyBuilderAccess.RunAndSave)
Dim myModBldr As ModuleBuilder = _
myAsmBldr.DefineDynamicModule(myAsmName.Name, _
myAsmName.Name & ".dll")
Dim myTypeBldr As TypeBuilder = myModBldr.DefineType("Adder")
Dim adderParams() As Type = {GetType(Integer), GetType(Integer)}
' This method will add two numbers which are 100 or less. If either of the
' passed integer vales are greater than 100, it will throw an exception.
Dim adderBldr As MethodBuilder = myTypeBldr.DefineMethod("DoAdd", _
MethodAttributes.Public Or MethodAttributes.Static, _
GetType(Integer), adderParams)
Dim adderIL As ILGenerator = adderBldr.GetILGenerator()
' Types and methods used in the code to throw, catch, and
' display OverflowException. Note that if the catch block were
' for a more general type, such as Exception, we would need
' a MethodInfo for that type's ToString method.
'
Dim overflow As Type = GetType(OverflowException)
Dim exCtorInfo As ConstructorInfo = overflow.GetConstructor( _
New Type() {GetType(String)})
Dim exToStrMI As MethodInfo = overflow.GetMethod("ToString")
Dim writeLineMI As MethodInfo = GetType(Console).GetMethod("WriteLine", _
New Type() {GetType(String), _
GetType(Object)})
Dim tmp1 As LocalBuilder = adderIL.DeclareLocal(GetType(Integer))
Dim tmp2 As LocalBuilder = adderIL.DeclareLocal(overflow)
' In order to successfully branch, we need to create labels
' representing the offset IL instruction block to branch to.
' These labels, when the MarkLabel(Label) method is invoked,
' will specify the IL instruction to branch to.
'
Dim failed As Label = adderIL.DefineLabel()
Dim endOfMthd As Label = adderIL.DefineLabel()
' Begin the try block.
Dim exBlock As Label = adderIL.BeginExceptionBlock()
' First, load argument 0 and the integer value of "100" onto the
' stack. If arg0 > 100, branch to the label "failed", which is marked
' as the address of the block that throws an exception.
'
adderIL.Emit(OpCodes.Ldarg_0)
adderIL.Emit(OpCodes.Ldc_I4_S, 100)
adderIL.Emit(OpCodes.Bgt_S, failed)
' Now, check to see if argument 1 was greater than 100. If it was,
' branch to "failed." Otherwise, fall through and perform the addition,
' branching unconditionally to the instruction at the label "endOfMthd".
'
adderIL.Emit(OpCodes.Ldarg_1)
adderIL.Emit(OpCodes.Ldc_I4_S, 100)
adderIL.Emit(OpCodes.Bgt_S, failed)
adderIL.Emit(OpCodes.Ldarg_0)
adderIL.Emit(OpCodes.Ldarg_1)
adderIL.Emit(OpCodes.Add_Ovf_Un)
' Store the result of the addition.
adderIL.Emit(OpCodes.Stloc_S, tmp1)
adderIL.Emit(OpCodes.Br_S, endOfMthd)
' If one of the arguments was greater than 100, we need to throw an
' exception. We'll use "OverflowException" with a customized message.
' First, we load our message onto the stack, and then create a new
' exception object using the constructor overload that accepts a
' string message.
adderIL.MarkLabel(failed)
adderIL.Emit(OpCodes.Ldstr, "Cannot accept values over 100 for add.")
adderIL.Emit(OpCodes.Newobj, exCtorInfo)
' Throw the exception now on the stack.
adderIL.ThrowException(overflow)
' Start the catch block for OverflowException.
'
adderIL.BeginCatchBlock(overflow)
' When we enter the catch block, the thrown exception
' is on the stack. Store it, then load the format string
' for WriteLine.
'
adderIL.Emit(OpCodes.Stloc_S, tmp2)
adderIL.Emit(OpCodes.Ldstr, "Caught {0}")
' Push the thrown exception back on the stack, then
' call its ToString() method. Note that if this catch block
' were for a more general exception type, like Exception,
' it would be necessary to use the ToString for that type.
'
adderIL.Emit(OpCodes.Ldloc_S, tmp2)
adderIL.EmitCall(OpCodes.Callvirt, exToStrMI, Nothing)
' The format string and the return value from ToString() are
' now on the stack. Call WriteLine(string, object).
'
adderIL.EmitCall(OpCodes.Call, writeLineMI, Nothing)
' Since our function has to return an integer value, load -1 onto
' the stack to indicate an error, and store it in local variable
' tmp1.
adderIL.Emit(OpCodes.Ldc_I4_M1)
adderIL.Emit(OpCodes.Stloc_S, tmp1)
' End the exception handling block.
adderIL.EndExceptionBlock()
' The end of the method. If no exception was thrown, the correct value
' will be saved in tmp1. If an exception was thrown, tmp1 will be equal
' to -1. Either way, we'll load the value of tmp1 onto the stack and return.
'
adderIL.MarkLabel(endOfMthd)
adderIL.Emit(OpCodes.Ldloc_S, tmp1)
adderIL.Emit(OpCodes.Ret)
Dim adderType As Type = myTypeBldr.CreateType()
Dim addIns As Object = Activator.CreateInstance(adderType)
Dim addParams(1) As Object
Console.Write("Enter an integer value: ")
addParams(0) = CType(Convert.ToInt32(Console.ReadLine()), Object)
Console.Write("Enter another integer value: ")
addParams(1) = CType(Convert.ToInt32(Console.ReadLine()), Object)
Console.WriteLine("If either integer was > 100, an exception will be thrown.")
Console.WriteLine("---")
Console.WriteLine("{0} + {1} = {2}", addParams(0), addParams(1), _
adderType.InvokeMember("DoAdd", BindingFlags.InvokeMethod, _
Nothing, addIns, addParams))
End Sub
End Class
输出:
Enter an integer value: 24 Enter another integer value: 101 If either integer was > 100, an exception will be thrown. --- Caught System.OverflowException: Arithmetic operation resulted in an overflow. at Adder.DoAdd(Int32 , Int32 ) 24 + 101 = -1