运算符?

[yyixin]

 
        private long ReadLong4(long offset)
        {
            long ret = 0;
            ipFile.Position = offset;
            ret |= (ipFile.ReadByte() & 0xFF);
            ret |= ((ipFile.ReadByte() << 8) & 0xFF00);
            ret |= ((ipFile.ReadByte() << 16) & 0xFF0000);
            ret |= ((ipFile.ReadByte() << 24) & 0xFF000000);
            return ret;
        }

在经符号扩展的操作数上使用了按位“或”运算符；请考虑首先强制转换为较小的无符号类型

出现如上警告，请问如何改？谢谢.

[yyixin]

up

[volnet]

ret |= (long)(ipFile.ReadByte() & 0xFF);

[CodingPioneer]

ret = (long)((UInt32)ret | (UInt32)(ipFile.ReadByte() & 0xFF));

[CodingPioneer]

更直接更好的方法
ret |= (long)(ipFile.ReadByte() & (long)0xFF);
ret |= ((ipFile.ReadByte() << 8) & (long)0xFF00);
ret |= ((ipFile.ReadByte() << 16) & (long)0xFF0000);
ret |= ((ipFile.ReadByte() << 24) & (long)0xFF000000);