.net 4.5是4.0的update，所以直接用4.0部署就可以了

.NET 4.5 is an in-place replacement for .NET 4.0，

When .NET 4.5 is installed it effectively replaces .NET 4.0 on the machine. .NET 4.0 gets overwritten by a new version of .NET 4.5 which - according to Microsoft - is supposed to be 100% backwards compatible.

我们简单的理解就是，4.5本质上还是4.0，属于递增式的更新，所以对IIS 来说看到的只有4.0而已，看看如下的4.5 DLL库中的版本号就知道了