记：

近期在C#中调用别人的DLL的时候有时候出现了 尝试读取或写入受保护的内存 。这通常指示其他内存已损坏 的问题。

错误类型：System.AccessViolationException。

问题位置：在与C++ dll规定传参的类型用的是string导致

　　问题原因：C++ string类的字符在内存的储存位置：数据<=16字节，在当前栈区；数据>16字节，在堆区

　　　　　　　C# string是存放在堆区的。

解决方案：在传值的时候用指针，再做转换就好了。

    public class APP_DLL
    {
        [DllImport("ruihua.dll", CallingConvention = CallingConvention.Cdecl)] //引入dll，并设置字符集
        public static extern int test(byte[] src1, int w1, int h1, int channel1, byte[] src2, int w2, int h2, int channel2, string str);
    }

改为：

    public class APP_DLL
    {
        [DllImport("ruihua.dll", CallingConvention = CallingConvention.Cdecl)] //引入dll，并设置字符集
        public static extern int test(byte[] src1, int w1, int h1, int channel1, byte[] src2, int w2, int h2, int channel2, IntPtr str);
    }

C# string转IntPtr方法：

　　IntPtr ptrIn = Marshal.StringToHGlobalAnsi(obj.ToString());

C# IntPtr转string方法：

　　string retlust = Marshal.PtrToStringAnsi(ptrIn);  

转之   https://www.cnblogs.com/mexihq/p/12696579.html

create table #Data(name varchar(100),row varchar(100),reserved varchar(100),data varchar(100),index_size varchar(100),unused varchar(100)) 
 
declare @name varchar(100) 
declare cur cursor  for 
    select name from sysobjects where xtype='u' order by name 
open cur 
fetch next from cur into @name 
while @@fetch_status=0 
begin 
    insert into #data 
    exec sp_spaceused   @name 
    print @name 
 
    fetch next from cur into @name 
end 
close cur 
deallocate cur 
 
create table #DataNew(name varchar(100),row int,reserved int,data int,index_size int,unused int) 
 
insert into #dataNew 
select name,convert(int,row) as row,convert(int,replace(reserved,'KB','')) as reserved,convert(int,replace(data,'KB','')) as data, 
convert(int,replace(index_size,'KB','')) as index_size,convert(int,replace(unused,'KB','')) as unused from #data  
 
select * from #dataNew order by data desc