Question

我正在尝试从结构中获取数组值的字段信息。到目前为止，我有以下内容，但我没有看到如何获得我想要的信息。

    [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
        }
    }

所以如果我这样做了：

 Type array_type = struct_field.FieldType.GetElementType();

这将返回Test2类型，但我不想要数组的类型，我想要FieldInfo或该结构的Fields，以便我可以在其中设置值。

Answer 1

你到底在追求什么？对于数组中的项，没有FieldInfo ...您可以通过获取数组（作为Array）并迭代它来迭代值...只需使用：

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

Answer 2

抱歉最初的错误答案。我懒得创建自己的Test2类型，所以我用了一个字符串代替。这是正确的答案（希望如此）：

我用以下代码做了你想做的事情：

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;
}

这是最重要的一句话：

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

它应该为您提供您正在谈论的FieldInfo。

Answer 3

@ weiqure技术的问题在于它只有在数组中至少有一个元素时才有效。这是一种查找数组元素类型的方法，无论它是否包含元素：

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;
}

以下是您将如何使用该功能：

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

如何获取数组字段的FieldInfo？

3 个答案: