在C#中調用Java代碼并處理多態，可以通過以下步驟實現：

1. 首先，確保你已經將Java類庫添加到C#項目中。可以使用Java Native Interface (JNI)或者Java Native Access (JNA)來實現這一點。這里我們以JNI為例。

2. 在Java中定義一個具有多態性的類。例如，我們定義一個Animal類和一個Dog類，Dog類繼承自Animal類：

// Animal.java
public class Animal {
    public void makeSound() {
        System.out.println("The animal makes a sound");
    }
}

// Dog.java
public class Dog extends Animal {
    @Override
    public void makeSound() {
        System.out.println("The dog barks");
    }
}

3. 使用javac命令編譯Java類，并使用javah命令生成JNI頭文件：

javac Animal.java Dog.java
javah -jni Animal

4. 創建一個C#項目，并使用DllImport屬性導入Java類庫。然后，使用CSharpJavaClass類加載Java類，并調用多態方法：

using System;
using System.Runtime.InteropServices;

class Program
{
    static void Main()
    {
        // 加載Java類庫
        IntPtr javaLibrary = LoadJavaLibrary();

        // 創建Java對象
        IntPtr animalHandle = CreateJavaObject(javaLibrary, "Animal");
        IntPtr dogHandle = CreateJavaObject(javaLibrary, "Dog");

        // 調用多態方法
        CallMethod(animalHandle, "makeSound"); // 輸出 "The animal makes a sound"
        CallMethod(dogHandle, "makeSound");   // 輸出 "The dog barks"

        // 釋放資源
        ReleaseJavaObject(animalHandle);
        ReleaseJavaObject(dogHandle);
        FreeJavaLibrary(javaLibrary);
    }

    static IntPtr LoadJavaLibrary()
    {
        return NativeMethods.LoadLibrary("path/to/your/java_library.so");
    }

    static IntPtr CreateJavaObject(IntPtr library, string className)
    {
        return NativeMethods.CreateObject(library, className);
    }

    static void CallMethod(IntPtr objectHandle, string methodName)
    {
        NativeMethods.CallMethod(objectHandle, methodName);
    }

    static void ReleaseJavaObject(IntPtr objectHandle)
    {
        NativeMethods.ReleaseObject(objectHandle);
    }

    static void FreeJavaLibrary(IntPtr library)
    {
        NativeMethods.FreeLibrary(library);
    }
}

public static class NativeMethods
{
    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr LoadLibrary(string dllToLoad);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr CreateObject(IntPtr library, string className);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern void CallMethod(IntPtr objectHandle, string methodName);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern void ReleaseObject(IntPtr objectHandle);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern bool FreeLibrary(IntPtr hModule);
}

注意：請將path/to/your/java_library.so替換為實際的Java類庫路徑。

通過以上步驟，你可以在C#中調用Java代碼并處理多態。