So you thought your server is running Asp.Net 4.5 or higher, but when you look at the .Net Framework version from your application or the Admin it still says 4.0 (and then some numbers)?  Is something wrong?

No. For whatever reason, Microsoft version numbers shown on asp.net web pages might not be what you would expect.  It's not you, it's not your server, it's Microsoft way of handling numbers for 4.5 and higher.  

For example, you might use code like this <%=Environment.Version%> in an Asp.Net page to check the version. While it may say you are running version 4.0, you might actually be running 4.5, 4.5.1, 4.5.2 or higher...

Here is a breakdown of what version you have running.

.NET 4.0 says 4.0.30319.0 to 4.0.30319.17000
.NET 4.5 says 4.0.30319.17001 to 4.0.30319.18400
.NET 4.5.1 says 4.0.30319.18401 to 4.0.30319.34000
.NET 4.5.2 says 4.0.30319.34000 to [unknown as of yet]

In other words....

If it says 4.0.30319.0 to 4.0.30319.17000 your server is running .NET 4.0

If it says 4.0.30319.17001 to 4.0.30319.18400 your server is running .NET 4.5

If it says 4.0.30319.18401 to 4.0.30319.34000 your server is running .NET 4.5.1

If it says From 4.0.30319.34000 your server is running .NET 4.5.2

In conclusion, if your server is running anything less than 4.0, you should immediately install the latest .Net framework 4.5.