See my tip for an Inno Setup example with SQL Server Express:
Inno Setup Script to Install SQL Server 2008 R2 with Tools[
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I would not recommend adding the .NET framework to your setup, but if you must
two types of redistributable installations for framework 4.5 are available:
1. Web installer (requires internet connection)
2. Offline installer
These can be found on:
Installing the .NET Framework[
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I would not recommend using the offline installer however, the web installer seems to do a better job to install missing parts.