define class 定义类 ？

是的

能不能举个可用的例子
我之前也想这么用过
但一直没有成功

你想要怎样的例子，楼主的问题也没有上传相应的DLL。

调用带结构体参数的windows api就可以
随便哪个函数都行

CLEAR ALL
CLEAR
DECLARE GetSystemInfo IN WIN32API String @
cBuffer = SPACE(40)
GetSystemInfo(@cBuffer)
SystemInfo = CREATEOBJECT("_SystemInfo", @cBuffer)
? "处理器类型: " + TRANSFORM(SystemInfo.ProcessorType)
? "处理器个数: " + TRANSFORM(SystemInfo.NumberOfProcessors)
? "处理器架构: " + SystemInfo.ProcessorArchitecture
? "内存页大小: " + TRANSFORM(SystemInfo.PageSize)
? "可用内存起始地址: " + TRANSFORM(SystemInfo.MinimumApplicationAddress)
? "可用内存结束地址: " + TRANSFORM(SystemInfo.MaximumApplicationAddress)
RETURN 

DEFINE CLASS _SystemInfo AS Custom

    OemID = SPACE(4)
    ProcessorArchitecture = ""
    PageSize = 0
    MinimumApplicationAddress = 0
    MaximumApplicationAddress = 0
    ActiveProcessorMask = SPACE(4)
    NumberOfProcessors = 0
    ProcessorType = 0
    AllocationGranularity = SPACE(4)
    ProcessorLevel = SPACE(2)
    ProcessorRevision = SPACE(2)
   
    PROCEDURE Init(tcString)
        WITH This
            .NumberOfProcessors = CTOBIN(SUBSTR(tcString, 21, 4), "4RS")
            .ProcessorType = CTOBIN(SUBSTR(tcString, 25, 4), "4RS")
            LOCAL lnTemp
            lnTemp = CTOBIN(SUBSTR(tcString, 7, 2), "2RS")
            DO CASE
                CASE lnTemp == 0
                    .ProcessorArchitecture = "INTEL"
                CASE lnTemp == 6
                    .ProcessorArchitecture == "IA64"
                CASE lnTemp == 9
                    .ProcessorArchitecture = "AMD64"
                otherwise
                    .ProcessorArchitecture = "UNKNOWN"  
            ENDCASE
            .PageSize = CTOBIN(SUBSTR(tcString, 9, 4), "4RS")
            .MinimumApplicationAddress = CTOBIN(SUBSTR(tcString, 13, 4), "4RS")
            .MaximumApplicationAddress = CTOBIN(SUBSTR(tcString, 17, 4), "4RS")
        ENDWITH
    ENDPROC
   
ENDDEFINE

我的这个DLL是一个外部设备带的，其他机器无法测试，是通过这个外设取得一些信息以这个结构传递给调用者。我就是想问在VFP里怎么实现这种结构，并且调用的时候参数传递上要注意些什么。我用STRING类型试过，只能取到第一个变更name的数据，之后就报错，我猜测是不是结构在存储时有分隔符，string读不到后面的

C字符串当然有分隔符。看看你的代码。

看哪个代码？DLL的？厂家没给

看你使用的代码，你自己描述的不清楚。