我有一个很长的字符串，按照以下模式分成了许多较小的字符串：
Public Class Test
Public Prefix_1 as String = "1 to 100 bytes"
Public Prefix_2 as String = "101 to 200 bytes"
Public Prefix_3 as String = "201 to 300 bytes"
Public Prefix_4 as String = "301 to 400 bytes"
'and so on
End Class
这个测试类已经编译为类库项目（即.dll文件）并保存在C：\ Test.dll中。
请注意，我事先不知道dll文件中有多少个Prefix_字符串。
我的问题是：如何通过反射检索所有以Prefix_ 开头的字符串，并按升序连接它们（即Prefix_1＆Prefix_2 ...）成一个字符串？
悬赏更新：
悬赏仅适用于VB.NET解决方案的答案
这应该能帮助您入门。很抱歉它是C#，但我不记得lambda语法。
Type type = Assembly.LoadFrom (@"c:\test.dll").GetType ("Test");
object instance = type.GetConstructor (Type.EmptyTypes).Invoke (null);
var fields = type.GetFields ().Where (f => f.Name.StartsWith ("Prefix_")).OrderBy(f => f.Name);
string x = fields.Aggregate (new StringBuilder (), (sb, f) => sb.Append((string)f.GetValue (instance)), sb => sb.ToString ());
VB.NET
Dim type As Type = Assembly.LoadFrom("c:\test.dll").GetType("Test")
Dim instance As Object = Type.GetConstructor(Type.EmptyTypes).Invoke(Nothing)
Dim fields = _
type.GetFields() _
.Where(Function(f) f.Name.StartsWith("Prefix_")) _
.OrderBy(Function(f) f.Name)
Dim bigString As String = _
fields.Aggregate(New StringBuilder(), _
Function(sb, f) sb.Append(DirectCast(f.GetValue(instance), String)), _
Function(sb) sb.ToString())
Type.GeConstructor().Invoke() 而不是 Activator.CreateInstance()？此外，如果字段命名为例如 Prefix_9 和 Prefix_10，则这种方法将无法正常工作。 - svickImplements IComparable to centralize sorting logic in one place (it's based on the field number)
Imports System.Reflection
Friend Class StringChunkField
Implements IComparable(Of StringChunkField)
#Region "Fields"
Private ReadOnly _number As Integer
Private _name As String
Private _stringChunk As String
Private Shared _beginningOfStringFieldNumber As Integer = 1
Private Shared _namePrefix As String = "Prefix_"
#End Region
Public Sub New(ByRef field As FieldInfo, ByRef target As Object)
_name = field.Name
_stringChunk = field.GetValue(target)
_number = ExtractFieldNumber(field.Name)
End Sub
#Region "Properties"
' Returns the field's number
Public ReadOnly Property Number() As Integer
Get
Return _number
End Get
End Property
' Returns the field's name (includes the number also)
Public ReadOnly Property Name() As String
Get
Return _name
End Get
End Property
' Returns the chunk of the string this fields holds
Public ReadOnly Property StringChunk() As String
Get
Return _stringChunk
End Get
End Property
' Returns the number of characters held in this field
Public ReadOnly Property NumberOfCharacters() As Integer
Get
If (String.IsNullOrEmpty(StringChunk)) Then
Return 0
Else
Return StringChunk.Length
End If
End Get
End Property
Public Shared ReadOnly Property BeginningOfStringFieldNumber() As String
Get
Return _beginningOfStringFieldNumber
End Get
End Property
#End Region
#Region "Comparison"
Public Function CompareTo(ByVal other As StringChunkField) As Integer Implements IComparable(Of StringChunkField).CompareTo
Return Number.CompareTo(other.Number)
End Function
Function IsFollowedBy(ByVal other As StringChunkField) As Object
Return other.Number = Number + 1
End Function
#End Region
#Region "Testing"
Public Function HoldsBeginingOfTheString() As Boolean
Return Number = 1
End Function
Public Shared Function IsPrefixField(ByVal field As FieldInfo) As Boolean
Return field.Name.StartsWith(_namePrefix)
End Function
#End Region
Private Function ExtractFieldNumber(ByVal fieldName As String) As Integer
Dim fieldNumber As String = fieldName.Replace(_namePrefix, String.Empty)
Return Integer.Parse(fieldNumber)
End Function
End Class
StringChunkField，使用什么名称前缀以及如何构建它，我们可以使用TypeEmbeddedStringReader类的实例查询对象包含的字符串。StringChunkFields presents in an objectStringChunkField and if the numbers are consecutiveRebuild the embedded string in the object from the StringChunkFields values
Imports System.Reflection
Imports System.Text
Public Class TypeEmbeddedStringReader
Public Shared Function ReadStringFrom(ByRef target As Object) As String
' Get all prefix fields from target
' Each StringChunkField hold a chunk of the String to rebuild
Dim prefixFields As IEnumerable(Of StringChunkField) = GetPrefixFieldsFrom(target)
' There must be, at least, one StringChunkField
ValidateFieldsFound(prefixFields)
' The first StringChunkField must hold the beggining of the string (be numbered as one)
ValidateFieldNumbersBeginAtOne(prefixFields)
' Ensure that no StringChunkField number were skipped
ValidateFieldNumbersAreConsecutive(prefixFields)
' Calculate the total number of chars of the string to rebuild to initialize StringBuilder and make it more efficient
Dim totalChars As Integer = CalculateTotalNumberOfCharsIn(prefixFields)
Dim result As StringBuilder = New StringBuilder(totalChars)
' Rebuild the string
For Each field In prefixFields
result.Append(field.StringChunk)
Next
' We're done
Return result.ToString()
End Function
#Region "Validation"
Private Shared Sub ValidateFieldsFound(ByVal fields As List(Of StringChunkField))
If (fields.Count = 0) Then Throw New ArgumentException("Does not contains any StringChunkField", "target")
End Sub
Private Shared Sub ValidateFieldNumbersBeginAtOne(ByVal fields As List(Of StringChunkField))
' Get the first StringChunkField found
Dim firstStringChunkField As StringChunkField = fields.First
' If does not holds the begining of the string...
If (firstStringChunkField.HoldsBeginingOfTheString() = False) Then
' Throw an exception with a meaningful error message
Dim invalidFirstPrefixField = String.Format("The first StringChunkField found, '{0}', does not holds the beggining of the string. If holds the beggining of the string, it should be numbered as '{1}'.", firstStringChunkField.Name, StringChunkField.BeginningOfStringFieldNumber)
Throw New ArgumentException(invalidFirstPrefixField, "target")
End If
End Sub
Private Shared Sub ValidateFieldNumbersAreConsecutive(ByVal fields As List(Of StringChunkField))
For index = 0 To fields.Count - 2
' Get the current and next field in fields
Dim currentField As StringChunkField = fields(index)
Dim nextField As StringChunkField = fields(index + 1)
' If the numbers are consecutive, continue checking
If (currentField.IsFollowedBy(nextField)) Then Continue For
' If not, throw an exception with a meaningful error message
Dim missingFieldMessage As String = String.Format("At least one StringChunkField between '{0}' and '{1}' is missing", currentField.Name, nextField.Name)
Throw New ArgumentException(missingFieldMessage, "target")
Next
End Sub
#End Region
Private Shared Function CalculateTotalNumberOfCharsIn(ByVal fields As IEnumerable(Of StringChunkField)) As Integer
Return fields.Sum(Function(field) field.NumberOfCharacters)
End Function
Private Shared Function GetPrefixFieldsFrom(ByVal target As Object) As List(Of StringChunkField)
' Find all fields int the target object
Dim fields As FieldInfo() = target.GetType().GetFields()
' Select the ones that are PrefixFields
Dim prefixFields As IEnumerable(Of StringChunkField) = From field In fields Where StringChunkField.IsPrefixField(field) Select New StringChunkField(field, target)
' Return the sorted list of StringChunkField found
Return prefixFields.OrderBy(Function(field) field).ToList()
End Function
End Class
用法
我准备了一些示例类型来测试 TypeEmbeddedStringReader 类的行为和使用方法。
简单来说，你需要调用 Shared 函数 ReadStringFrom 并传递一个包含要读取的字符串的对象作为参数。
以下是示例类型：
Public Class SampleType
Public Prefix_1 As String = "1 to 100 bytes"
Public Prefix_2 As String = "101 to 200 bytes"
Public Prefix_3 As String = "201 to 300 bytes"
Public Prefix_4 As String = "301 to 400 bytes"
End Class
Public Class TypeWithoutString
End Class
Public Class TypeWithNonConsecutiveFields
Public Prefix_1 As String = "1 to 100 bytes"
Public Prefix_5 As String = "101 to 200 bytes"
End Class
Public Class TypeWithInvalidStringBeginning
Public Prefix_2 As String = "1 to 100 bytes"
End Class
这是我用来测试的主要模块：
Imports TypeEmbeddedStringReader.Samples
Module Module1
Sub Main()
ExtractStringFrom(New TypeWithoutString())
ExtractStringFrom(New TypeWithInvalidStringBeginning())
ExtractStringFrom(New TypeWithNonConsecutiveFields())
ExtractStringFrom(New SampleType())
End Sub
Private Sub ExtractStringFrom(ByVal target As Object)
Try
Dim result As String = TypeEmbeddedStringReader.ReadStringFrom(target)
Console.WriteLine(result)
Catch exception As ArgumentException
Console.WriteLine("Type '{0}': {1}", target.GetType(), exception.Message)
End Try
Console.WriteLine()
End Sub
End Module
运行后的结果如下：
Type 'TypeEmbeddedStringReader.Samples.TypeWithoutString': Does not contains any StringChunkField
Parameter name: target
Type 'TypeEmbeddedStringReader.Samples.TypeWithInvalidStringBeginning': The first StringChunkField found, 'Prefix_2', does not holds the beggining of the string. If holds the beggining of the string, it should be numbered as '1'.
Parameter name: target
Type 'TypeEmbeddedStringReader.Samples.TypeWithNonConsecutiveFields': At least one StringChunkField between 'Prefix_1' and 'Prefix_5' is missing
Parameter name: target
1 to 100 bytes101 to 200 bytes201 to 300 bytes301 to 400 bytes
请告诉我这是否对您有用，如果需要其他帮助，请随时联系我。
更新
根据Gens的要求，我添加了一个功能到TypeEmbeddedStringReader类中，可以从提供类型名称和程序集文件的实例中读取字符串：
Public Shared Function ReadStringFromInstanceOf(ByRef assemblyFile As String, ByRef targetTypeName As String)
Dim assembly As Assembly = assembly.LoadFrom(assemblyFile)
Dim targetType As Type = assembly.GetType(targetTypeName)
Dim target As Object = Activator.CreateInstance(targetType)
Return ReadStringFrom(target)
End Function
这是我用于测试的样本类型：
Public Class UnorderedFields
Public Prefix_2 As String = "101 to 200 bytes"
Public Prefix_4 As String = "301 to 400 bytes"
Public Prefix_1 As String = "1 to 100 bytes"
Public Prefix_3 As String = "201 to 300 bytes"
End Class
Dim assemblyFile As String = Assembly.GetExecutingAssembly()
Dim targetTypeName As String = "TypeEmbeddedStringDemo.UnorderedFields"
Console.WriteLine(TypeEmbeddedStringReader.ReadStringFromInstanceOf(assemblyFile, targetTypeName))
1 to 100 bytes101 to 200 bytes201 to 300 bytes301 to 400 bytes
Public Class UnorderedFields
Public Prefix_2 As String = "101 to 200 bytes"
Public Prefix_11 As String = "301 to 400 bytes"
Public Prefix_1 As String = "1 to 100 bytes"
Public Prefix_3 As String = "201 to 300 bytes"
End Class
1 to 100 bytes**301 to 400 bytes**101 to 200 bytes201 to 300 bytes
Public Function Compare(ByVal x As FieldInfo, ByVal y As FieldInfo) As Integer Implements IComparer(Of FieldInfo).Compare
Dim xNumber = Integer.Parse(x.Name.Replace("Prefix_", String.Empty))
Dim yNumber = Integer.Parse(y.Name.Replace("Prefix_", String.Empty))
Return xNumber.CompareTo(yNumber)
End Function
产生正确的结果：
1 to 100 bytes101 to 200 bytes201 to 300 bytes301 to 400 bytes
Public Function Extract() As String
Dim type As Type = Assembly.LoadFrom("C:\test.dll").GetType("YourNamespace.Test")
Dim instance As Object = Activator.CreateInstance(type)
Dim sb As New StringBuilder
Dim field As FieldInfo
For Each field In type.GetFields
If field.Name.StartsWith("Prefix_") Then
sb.Append(field.GetValue(instance))
End If
Next
Return sb.ToString
End Function
otherwise here is a function with sorting:
Public Function Extract() As String
Dim type As Type = Assembly.LoadFrom("c:\test.dll").GetType("YourNamespace.Test")
Dim fields As New List(Of FieldInfo)
Dim field As FieldInfo
For Each field In type.GetFields
If field.Name.StartsWith("Prefix_") Then
fields.Add(field)
End If
Next
fields.Sort(New FieldComparer)
Dim sb As New StringBuilder
Dim instance As Object = Activator.CreateInstance(type)
For Each field In fields
sb.Append(field.GetValue(instance))
Next
Return sb.ToString
End Function
Private Class FieldComparer
Implements IComparer(Of FieldInfo)
Public Function Compare(ByVal x As FieldInfo, ByVal y As FieldInfo) As Integer Implements IComparer(Of FieldInfo).Compare
Return x.Name.CompareTo(y.Name)
End Function
End Class
Test myTestInstance = ... // Do stuff to the the instance of your class
Type myType = typeof(Test); // Or call GetType() on an instance
FieldInfo[] myFields = myType.GetFields();
var myPrefixedFields = myFields
.Where(fi => fi.Name.StartsWith("Prefix_"))
.OrderBy(fi => fi.Name);
string result = string.Empty;
foreach(FieldInfo fi in myPrefixedFields)
{
// You may prefer to use a string builder.
result += fi.GetValue(myTestInstance);
}
大概就是这样了。
以下是 C# 代码（VB.NET 稍微生疏一点 :)):
using System;
using System.Linq;
using System.Text;
using System.Reflection;
void ExtractFields()
{
const string prefix = "Prefix_";
Assembly assembly = Assembly.LoadFile("C:\\Test.dll");
Type classTestType = assembly.GetType("Test");
var classTest = Activator.CreateInstance(classTestType);
FieldInfo[] fields = classTestType.GetFields(BindingFlags.GetField)
.Where(m => m.Name.StartsWith(prefix))
.OrderBy(m => m.Name)
.ToArray();
var sb = new StringBuilder();
foreach (FieldInfo field in fields)
{
sb.Append(field.GetValue(classTest));
}
string allStringConcatenated = sb.ToString();
}
使用一个稍作修改的测试类，来自您的问题：
Public Class Test
Public Prefix_15 As String = "501 to 600 bytes"
Public Prefix_5 As String = "401 to 500 bytes"
Public Prefix_1 As String = "1 to 100 bytes"
Public Prefix_2 As String = "101 to 200 bytes"
Public Prefix_3 As String = "201 to 300 bytes"
Public Prefix_4 As String = "301 to 400 bytes"
End Class
Public Function GetPrefixString() As String
Dim type As Type = Assembly.LoadFrom("C:\test.dll").GetType("Test.Test")
Dim test As Object = Activator.CreateInstance(type)
Dim fieldList As New List(Of String)
For Each field As FieldInfo In _
From x In type.GetFields _
Where x.Name.StartsWith("Prefix_") _
Order By Convert.ToInt32(x.Name.Replace("Prefix_", String.Empty))
fieldList.Add(field.GetValue(test))
Next
Return String.Join(String.Empty, fieldList.ToArray)
End Sub
产生以下结果：
1到100字节101到200字节201到300字节301到400字节401到500字节501到600字节