如何在 C# 中将 DLLImport 与结构一起用作参数？
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How do I use DLLImport with structs as parameters in C#?
提问by Jonathan Beerhalter
All the examples I can find using DLLImport to call C++ code from C# passes ints back and forth. I can get those examples working just fine. The method I need call takes two structs as its import parameters, and I'm not exactly clear how I can make this work.
我能找到的所有使用 DLLImport 从 C# 调用 C++ 代码的示例都来回传递整数。我可以让这些例子工作得很好。我需要调用的方法将两个结构体作为其导入参数，我不太清楚如何进行这项工作。
Here's what I've got to work with:
这是我必须使用的：
I own the C++ code, so I can make any changes/additions to it that I need to.
我拥有 C++ 代码，因此我可以对其进行任何需要的更改/添加。
A third party application is going to load my DLL on startup and expects the DLLExport to be defined a certain way, so i can't really change the method signature thats getting exported.
第三方应用程序将在启动时加载我的 DLL 并期望以某种方式定义 DLLExport，因此我无法真正更改导出的方法签名。
The C# app I'm building is going to be used as a wrapper so i can integrate this C++ piece into some of our other applications, which are all written in C#.
我正在构建的 C# 应用程序将用作包装器，因此我可以将这个 C++ 部分集成到我们的其他一些应用程序中，这些应用程序都是用 C# 编写的。
The C++ method signature I need to call looks like this
我需要调用的 C++ 方法签名如下所示
DllExport int Calculate (const MathInputStuctType *input,
MathOutputStructType *output, void **formulaStorage)
And MathInputStructType is defined as the following
并且 MathInputStructType 定义如下
typedef struct MathInputStuctTypeS {
int _setData;
double _data[(int) FieldSize];
int _setTdData;
} MathInputStuctType;
采纳答案by Jim Mischel
The MSDN topic Passing Structureshas a good introduction to passing structures to unmanaged code. You'll also want to look at Marshaling Data with Platform Invoke, and Marshaling Arrays of Types.
MSDN 主题传递结构很好地介绍了将结构传递给非托管代码。您还需要查看使用 Platform Invoke和Marshaling Arrays of Types编组数据。
回答by casperOne
From the declaration you posted, your C# code will look something like this:
根据您发布的声明，您的 C# 代码将如下所示：
[DllImport("mydll.dll")]
static extern int Calculate(ref MathInputStructType input,
ref MathOutputStructType output, ref IntPtr formulaStorage);
Depending on the structure of MathInputStructType and MathOutputStructType in C++, you are going to have to attribute those structure declarations as well so that they marshal correctly.
根据 C++ 中 MathInputStructType 和 MathOutputStructType 的结构，您还必须对这些结构声明进行属性化，以便它们正确编组。
回答by leppie
For the struct:
对于结构：
struct MathInputStuctType
{
int _setData;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = FieldSize)]
double[] _data;
int _setTdData;
}
回答by LanceSc
You might want to look at this project on CodePlex, http://www.codeplex.com/clrinterop/Release/ProjectReleases.aspx?ReleaseId=14120. It should help you marshal the structures correctly.
您可能想在 CodePlex 上查看这个项目，http://www.codeplex.com/clrinterop/Release/ProjectReleases.aspx? ReleaseId =14120 。它应该可以帮助您正确编组结构。
