通过反编译让SpecFlow支持多层属性值的验证

需求：在使用SpecFlow时，我希望能对目标对象所关联的对象属性进行验证，但SpecFlow（Version 1.9.0）无法实现。如图中红框，可以对专户所属的金融机构的名称进行验证。

反编译步骤

1. 利用ildasm（.net自带）反编译 TechTalk.SpecFlow.dll 生成IL中间代码 一般会生成 *.il 和*.res 一些其它资源文件 *.resources；
2. 然后用记事本修改IL文件；
3. 然后用ilasm编译中间代码，生成新的 TechTalk.SpecFlow.dll 文件；
4. 删除签名。

　　详细步骤见参考文献[1]

修改前后代码对比

第一处修改

TechTalk.SpecFlow.Assist.TEHelpers 类的 IsPropertyMatchingToColumnName 方法，带“.”的列名不验证是否存在对应的属性。

// 修改前的源代码
1 internal static bool IsPropertyMatchingToColumnName(PropertyInfo property, string columnName)
 {
     return property.Name.MatchesThisColumnName(columnName);
 }

 // 修改前的中间语言
 1 .method assembly hidebysig static bool  IsPropertyMatchingToColumnName(class [mscorlib]System.Reflection.PropertyInfo 'property',
                                                                        string columnName) cil managed
 {
   // Code size       13 (0xd)
   .maxstack
   IL_0000:  ldarg.
   IL_0001:  callvirt   instance string [mscorlib]System.Reflection.MemberInfo::get_Name()
   IL_0006:  ldarg.
   IL_0007:  call       bool TechTalk.SpecFlow.Assist.TEHelpers::MatchesThisColumnName(string,
                                                                                       string)
   IL_000c:  ret
 } // end of method TEHelpers::IsPropertyMatchingToColumnName

// 修改后的源代码
1 internal static bool IsPropertyMatchingToColumnName(PropertyInfo property, string columnName)
 {
     return ((columnName.IndexOf('.') > -) || property.Name.MatchesThisColumnName(columnName));
 }

 // 修改后的中间语言
 1 .method assembly hidebysig static bool  IsPropertyMatchingToColumnName(class [mscorlib]System.Reflection.PropertyInfo 'property',
                                                                        string columnName) cil managed
 {
   // Code size       40 (0x28)
   .maxstack
   .locals init (bool V_0,
            bool V_1)
   IL_0000:  nop
   IL_0001:  ldarg.
   IL_0002:  ldc.i4.s
   IL_0004:  callvirt   instance int32 [mscorlib]System.String::IndexOf(char)
   IL_0009:  ldc.i4.m1
   IL_000a:  cgt
   IL_000c:  ldc.i4.
   IL_000d:  ceq
   IL_000f:  stloc.
   IL_0010:  ldloc.
   IL_0011:  brtrue.s   IL_0017
   IL_0013:  ldc.i4.
   IL_0014:  stloc.
   IL_0015:  br.s       IL_0026
   IL_0017:  ldarg.
   IL_0018:  callvirt   instance string [mscorlib]System.Reflection.MemberInfo::get_Name()
   IL_001d:  ldarg.
   IL_001e:  call       bool TechTalk.SpecFlow.Assist.TEHelpers::MatchesThisColumnName(string,
                                                                                       string)
   IL_0023:  stloc.
   IL_0024:  br.s       IL_0026
   IL_0026:  ldloc.
   IL_0027:  ret
 } // end of method TEHelpers::IsPropertyMatchingToColumnName

第二处修改

TechTalk.SpecFlow.Assist.PropertyExtensionMethods 类的 GetPropertyValue 方法，将属性名根据“.”分割后，循环获取关联对线的属性值。

// 修改前的源代码
1 public static object GetPropertyValue(this object @object, string propertyName)
 {
     return GetThePropertyOnThisObject(@object, propertyName).GetValue(@object, null);
 }

 // 修改前的中间语言
 1 .method public hidebysig static object  GetPropertyValue(object 'object',
                                                          string propertyName) cil managed
 {
   .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = (     )
   // Code size       17 (0x11)
   .maxstack
   .locals init (class [mscorlib]System.Reflection.PropertyInfo V_0)
   IL_0000:  ldarg.
   IL_0001:  ldarg.
   IL_0002:  call       class [mscorlib]System.Reflection.PropertyInfo TechTalk.SpecFlow.Assist.PropertyExtensionMethods::GetThePropertyOnThisObject(object,
                                                                                                                                                     string)
   IL_0007:  stloc.
   IL_0008:  ldloc.
   IL_0009:  ldarg.
   IL_000a:  ldnull
   IL_000b:  callvirt   instance object [mscorlib]System.Reflection.PropertyInfo::GetValue(object,
                                                                                           object[])
   IL_0010:  ret
 } // end of method PropertyExtensionMethods::GetPropertyValue

// 修改后的源代码
1 public static object GetPropertyValue(this object @object, string propertyName)
 {
     foreach (string str in propertyName.Split(new char[] { '.' }, StringSplitOptions.RemoveEmptyEntries))
     {
         @object = GetThePropertyOnThisObject(@object, str).GetValue(@object, null);
     }
     return @object;
 }

 // 修改后的中间语言
 1 .method public hidebysig static object  GetPropertyValue(object 'object',
                                                          string propertyName) cil managed
 {
   .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = (     )
   // Code size       64 (0x40)
   .maxstack
   .locals init (string[] V_0,
            string V_1,
            char[] V_2,
            string[] V_3,
            int32 V_4)
   IL_0000:  ldarg.
   IL_0001:  ldc.i4.
   IL_0002:  newarr     [mscorlib_6]System.Char
   IL_0007:  stloc.
   IL_0008:  ldloc.
   IL_0009:  ldc.i4.
   IL_000a:  ldc.i4.s
   IL_000c:  stelem.i2
   IL_000d:  ldloc.
   IL_000e:  ldc.i4.
   IL_000f:  callvirt   instance string[] [mscorlib_6]System.String::Split(char[],
                                                                           valuetype [mscorlib_6]System.StringSplitOptions)
   IL_0014:  stloc.
   IL_0015:  ldloc.
   IL_0016:  stloc.
   IL_0017:  ldc.i4.
   IL_0018:  stloc.s    V_4
   IL_001a:  br.s       IL_0037
   IL_001c:  ldloc.
   IL_001d:  ldloc.s    V_4
   IL_001f:  ldelem.ref
   IL_0020:  stloc.
   IL_0021:  ldarg.
   IL_0022:  ldloc.
   IL_0023:  call       class [mscorlib]System.Reflection.PropertyInfo TechTalk.SpecFlow.Assist.PropertyExtensionMethods::GetThePropertyOnThisObject(object,
                                                                                                                                                     string)
   IL_0028:  ldarg.
   IL_0029:  ldnull
   IL_002a:  callvirt   instance object [mscorlib_6]System.Reflection.PropertyInfo::GetValue(object,
                                                                                             object[])
   IL_002f:  starg.s    'object'
   IL_0031:  ldloc.s    V_4
   IL_0033:  ldc.i4.
   IL_0034:  add
   IL_0035:  stloc.s    V_4
   IL_0037:  ldloc.s    V_4
   IL_0039:  ldloc.
   IL_003a:  ldlen
   IL_003b:  conv.i4
   IL_003c:  blt.s      IL_001c
   IL_003e:  ldarg.
   IL_003f:  ret
 } // end of method PropertyExtensionMethods::GetPropertyValue

参考文献

[1] 编辑IL文件，修改DLL文件

[2] IL指令详细