定义一个float类型的变量=0.7，结果在IL中却是0.69999999。
乘以10之后，获取整数值。得到的却是6。通过查看IL，竟然被转换成double类型再转换。就变成6了。
Demo:
IL:
.method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// 代码大小 93 (0x5d)
.maxstack
//定义变量
.locals init ([] float32 val,
[] int32 i)
IL_0000: nop
IL_0001: ldc.r4 0.69999999
//将0.69999999赋值给第0个变量。明明定义的是0.7
IL_0006: stloc.
IL_0007: ldc.i4.s
/将10赋值给第一个变量
IL_0009: stloc.
//double类型的0.7
IL_000a: ldc.r8 0.69999999999999996
IL_0013: ldloc.
IL_0014: conv.r8
IL_0015: mul
IL_0016: call float64 [mscorlib]System.Math::Floor(float64)
IL_001b: call void [mscorlib]System.Console::WriteLine(float64)
IL_0020: nop
IL_0021: ldloc.
IL_0022: call void [mscorlib]System.Console::WriteLine(float32)
IL_0027: nop
//从堆栈中加载出val
IL_0028: ldloc.
//从堆栈中加载出i
IL_0029: ldloc.
//将i转换为float类型
IL_002a: conv.r4
//val*i
IL_002b: mul
//将乘法运算之后的结果转换为double类型
IL_002c: conv.r8
//调用Math.Floor对运算后的结果处理
IL_002d: call float64 [mscorlib]System.Math::Floor(float64)
IL_0032: call void [mscorlib]System.Console::WriteLine(float64)
IL_0037: nop
IL_0038: ldloc.
IL_0039: conv.r8
IL_003a: call void [mscorlib]System.Console::WriteLine(float64)
IL_003f: nop
IL_0040: ldloc.
IL_0041: ldloc.
IL_0042: conv.r4
IL_0043: mul
IL_0044: conv.r8
IL_0045: call void [mscorlib]System.Console::WriteLine(float64)
IL_004a: nop
IL_004b: ldloc.
IL_004c: conv.r8
IL_004d: ldloc.
IL_004e: conv.r8
IL_004f: mul
IL_0050: call void [mscorlib]System.Console::WriteLine(float64)
IL_0055: nop
IL_0056: call string [mscorlib]System.Console::ReadLine()
IL_005b: pop
IL_005c: ret
} // end of method Program::Main