Build error: “An expression is too long or complex to compile”

Question

Every now and then when I build a specific solution, I\'ll get a random amount of \"An expression is too long or complex to compile\" in the Error List window. However, the

Answer 1

When building you can see the the build output the last folder it checks before it fails. I removed the files in that folder and brought them back one by one. Finally found the issue. I dont know exactly what it is but it was a .aspx page with lots of HTML. It wasnt used often so I just removed it from the project and now it compiles.

Answer 2

I got this error in one project when I switched from Visual Studio 2012 to Visual Studio Community 2013. In my case it was giant file (25k lines, not written by me) with had List<string[]> initialized by collection initializer.

Something like this:

public class Class
{

    public List<string[]> BigList
    {
        get
        {
            return new List<string[]>()
            {
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                .
                .
                .
                .
                .
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"}
            }
        }
    }
}

I changed it to string[][] and the project started to compile

public class Class
{

    public string[][] BigList
    {
        get
        {
            return new string[][]
            {
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                .
                .
                .
                .
                .
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"},
                new string[]{"foo","bar"}
            }
        }
    }
}

Answer 3

I can share our experience with this error. Typical Microsoft masterpiece (or just a piece...) Our problem was actually due to too many DLLs for IIS to compile. Diagnosing it was a pain (as diagnostics is nonexistent). Removing some unnecessary DLLs (like unit test DLLs) from the main BIN folder has gotten rid of the problem. Go figure...

Answer 4

I have never seen this in the wild.

However, from googling around it may well be from an excess of assembly references, one particular quote:

If I reduce number of referenced assemblies to 5500 it is compiled and working

Now, surely, you would have noticed a dependency list that large, could you check whether you have an overly large number of assemblies referenced?

Answer 5

FYI, that error is characteristic of the compiler running out of stack space. Typically that happens when you throw a "deep recursion" problem at the compiler, like say,

int x = (1 + (1 + (1 + (1 + ......... + 1 ) + 1 ) + 1 ) + 1);

say, several thousand deep. The syntactic and semantic analyzers are both recursive-descent analyzers and therefore prone to running out of stack space in extreme scenarios.

I have no idea why shutting down and starting over would affect that, though. That is really strange.

If you get a solid repro, I'd love to see it. Either post it here, or enter a bug on Connect and we'll have a look at it. Without a solid repro though it is very hard to say what is going on here.

Answer 6

I had the same problem in a 64-bit machine (VS 2012).

I used @MikeFlynn's answer to locate the folder causing the error.

Finally I discovered I had a Help.aspx page with no code behind - just HTML but it had multiple icon images embedded as base 64

<img src="data:image/png;base64 ... />

I converted it to static HTML and it compiled.

P.S. The same project was compiling O.K. in a 32-bit VS2012 machine. Both machines were running Windows 7.