我如何获得一个数组字段的字段信息？

Question

我试图从一个结构内获得一个数组值的字段信息。到目前为止，我有以下的，但我没有看到如何得到我想要的infomration。

    [StructLayout(LayoutKind.Sequential)]
    public struct Test
    {
        public byte Byte1;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst=3)]
        public Test2[] Test1;
    }

    BindingFlags struct_field_flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly;
    FieldInfo[] all_struct_fields = typeof(Test).GetFields(struct_field_flags);
    foreach (FieldInfo struct_field in all_struct_fields)
    {
        if(struct_field.FieldType.IsArray)
        {
           // Get FieldInfo for each value in the Test1 array within Test structure
        }
    }

所以，如果我做的：

 Type array_type = struct_field.FieldType.GetElementType();

这将返回的Test2类型，但我不想要的阵列的类型，我想要的结构的字段信息或字段，以便可以通过在其内设置的值。

Answer 1

很抱歉的初始错误的答案。我才懒得创建自己的Test2类型，所以我用一个字符串代替。这里的正确答案（希望）：

我没有你想用下面的代码做什么：

class Program
{
    static void Main(string[] args)
    {
        object sampleObject = GetSampleObject();
        FieldInfo[] testStructFields = typeof(Test).GetFields();

        foreach (FieldInfo testStructField in testStructFields)
        {
            if (testStructField.FieldType.IsArray)
            {
                // We can cast to ILIst because arrays implement it and we verfied that it is an array in the if statement
                System.Collections.IList sampleObject_test1 = (System.Collections.IList)testStructField.GetValue(sampleObject);
                // We can now get the first element of the array of Test2s:
                object sampleObject_test1_Element0 = sampleObject_test1[0];

                // I hope this the FieldInfo that you want to get:
                FieldInfo myValueFieldInfo = sampleObject_test1_Element0.GetType().GetField("MyValue");

                // Now it is possible to read and write values
                object sampleObject_test1_Element0_MyValue = myValueFieldInfo.GetValue(sampleObject_test1_Element0);
                Console.WriteLine(sampleObject_test1_Element0_MyValue); // prints 99
                myValueFieldInfo.SetValue(sampleObject_test1_Element0, 55);
                sampleObject_test1_Element0_MyValue = myValueFieldInfo.GetValue(sampleObject_test1_Element0);
                Console.WriteLine(sampleObject_test1_Element0_MyValue); // prints 55
            }
        }
    }

    static object GetSampleObject()
    {
        Test sampleTest = new Test();
        sampleTest.Test1 = new Test2[5];
        sampleTest.Test1[0] = new Test2() { MyValue = 99 };
        object sampleObject = sampleTest;
        return sampleObject;
    }
}

[StructLayout(LayoutKind.Sequential)]
public struct Test2
{
    public int MyValue;
}

[StructLayout(LayoutKind.Sequential)]
public struct Test
{
    public byte Byte1;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
    public Test2[] Test1;
}

这是最重要的行：

FieldInfo myValueFieldInfo = sampleObject_test1_Element0.GetType().GetField("MyValue");

这应该给你，你正在谈论的字段信息。

Answer 2

究竟是什么，你以后？这里的是的无FieldInfo为阵...你可以通过获取阵列（如Array）迭代值，并在项目迭代...只是使用：

Array arr = (Array)field.GetValue(obj);

Answer 3

与@ weiqure的技术的问题是，如果在阵列已经具有在它的至少一种元素，它才有效。下面是一个方法来找到该数组元素类型，是否含有元素或不：

bool GetArrayElementType(FieldInfo field, out Type elementType)
{
    if (field.FieldType.IsArray && field.FieldType.FullName.EndsWith("[]"))
    {
        string fullName = field.FieldType.FullName.Substring(0, field.FieldType.FullName.Length - 2);
        elementType = Type.GetType(string.Format("{0},{1}", fullName, field.FieldType.Assembly.GetName().Name));
        return true;
    }
    elementType = null;
    return false;
}

这是你将如何使用该功能：

void Test(object targetObject, string fieldName)
{
    FieldInfo field = targetObject.GetType().GetField(fieldName);
    Type elementType;
    bool success = GetArrayElementType(field, out elementType);
}