title: What reference do I need to use Microsoft.Office.Interop.Excel in .NET?
body: <p>I am interested in using C# to manipulate/Automate Excel files.</p>
  
  <p>After browsing the web I have found <a href="http://msdn.microsoft.com/en-us/office/hh133430" rel="noreferrer">VSTO</a> but it seems you can not use that in Visual Studio Express Edition so I can not use that.</p>
  
  <p>Just few minutes ago I noticed a question in this site that used this namespace in its code:</p>
  
  <p><strong>Microsoft.Office.Interop.Excel</strong></p>
  
  <p>So I am wondering if all I need to use that is add necessary reference and if so which reference to add? </p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>I installed "Primary Interop Assemblies" as the accepted answer suggested but for some reason they are still missing in the Add Reference dialog under ".NET" but they are present in GAC. </p>
  
  <p>So I just added the reference using "Browse" and located <code>Microsoft.Office.Interop.Excel.dll</code> in GAC folder.</p>
  
  <p>But looking for similar questions on this site regarding adding reference from GAC it seems this is not recommended.</p>