CLR如何在内部将Double / Single转换为Decimal？

Question

I was interested to see how .NET converts Double/Single data types to Decimal , so I started Studying Decimal type struct source code that I came across to the code below.

It seems All other types conversions are implemented within framework's class library except double/float which are handled externally by CLR.

So, basically the question is How CLR does the Conversion?

    [MethodImpl(MethodImplOptions.InternalCall)]
    public extern Decimal(float value);

    [MethodImpl(MethodImplOptions.InternalCall)]
    public extern Decimal(double value);

    public Decimal(int value)
    {
        int num = value;
        if (num < 0)
        {
            this.flags = -2147483648;
            num = -num;
        }
        else
        {
            this.flags = 0;
        }
        this.lo = num;
        this.mid = 0;
        this.hi = 0;
    }

    [CLSCompliant(false)]
    public Decimal(uint value)
    {
        this.flags = 0;
        this.lo = (int)value;
        this.mid = 0;
        this.hi = 0;
    }

    .
    .
    .

Answer 1

While it is not as current as the latest CLR, the general details may be confirmed in the previously released SSCLI 2 (AKA Rotor ). The native portions of System.Decimal are implemented in clr\\src\\vm\\comdecimal.cpp. Each calls VarDecFromR4 and VarDecFromR8 , respectively. These are native APIs that are exposed by OleAut32.dll.

As for your next question: how does OleAut32 implement these functions? You're best bet is to attach a debugger and disassemble the functions. With WinDbg, you can do this with the uf command.