我有一个有趣的问题，使用的PInvoke在C＃中调用_snwprintf。它的工作原理为整数类型，但不为浮点数。

I am having an interesting problem with using pinvoke in C# to call _snwprintf. It works for integer types, but not for floating point numbers.

这是在64位的Windows，它工作正常在32位。

This is on 64-bit Windows, it works fine on 32-bit.

我的code是下面，请记住，这是一个人为的例子来说明，我看到的行为。

My code is below, please keep in mind that this is a contrived example to show the behavior I am seeing.

class Program
{
    [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
    private static extern int _snwprintf([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, IntPtr length, String format, int p);

    [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
    private static extern int _snwprintf([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, IntPtr length, String format, double p);

    static void Main(string[] args)
    {
        Double d = 1.0f;
        Int32 i = 1;
        Object o = (object)d;
        StringBuilder str = new StringBuilder(32);

        _snwprintf(str, (IntPtr)str.Capacity, "%10.1lf", (Double)o);
        Console.WriteLine(str.ToString());

        o = (object)i;
        _snwprintf(str, (IntPtr)str.Capacity, "%10d", (Int32)o);
        Console.WriteLine(str.ToString());

        Console.ReadKey();
    }
}

该程序的输出为

   0.0
     1

这应该打印1.0的第一线，而不是0.0，到目前为止，我难住了。

It should print 1.0 on the first line and not 0.0, and so far I am stumped.

推荐答案

我不完全相信你的话费为何不工作，但是的这些方法的安全版本不要在x86和x64的正常工作。

I'm not exactly sure why your calls do not work, but the secured versions of these methods do work properly in both x86 and x64.

下面code没有工作，符合市场预期：

The following code does work, as expected:

class Program
{
    [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
    private static extern int _snwprintf_s([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, IntPtr bufferSize, IntPtr length, String format, int p);

    [DllImport("msvcrt.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.Cdecl)]
    private static extern int _snwprintf_s([MarshalAs(UnmanagedType.LPWStr)] StringBuilder str, IntPtr bufferSize, IntPtr length, String format, double p);

    static void Main(string[] args)
    {
        // Preallocate this to a given length
        StringBuilder str = new StringBuilder(100);
        double d = 1.4;
        int i = 7;
        float s = 1.1f;

        // No need for box/unbox
        _snwprintf_s(str, (IntPtr)100, (IntPtr)32, "%10.1lf", d);
        Console.WriteLine(str.ToString());

        _snwprintf_s(str, (IntPtr)100, (IntPtr)32, "%10.1f", s);
        Console.WriteLine(str.ToString());

        _snwprintf_s(str, (IntPtr)100, (IntPtr)32, "%10d", i);
        Console.WriteLine(str.ToString());

        Console.ReadKey();
    }
}