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I am using Visual studio 2013 on Windows 7 64-bit with Office 2007 32-bit.

I have a c# WCF service library project which is trying to read data from an excel file as follows:

string con = @"Provider=Microsoft.ACE.OLEDB.12.0;" +
@"Data Source=c:\temp\Book2.xlsx;" +
@"Extended Properties='Excel 8.0;HDR=Yes; IMEX=1;'";

using (OleDbConnection connection = new OleDbConnection(con))
OleDbCommand command = new OleDbCommand("select * from [Sheet1$]", connection);
var TranArr = new string[999, 20];
using (OleDbDataReader dr = command.ExecuteReader())
{ etc...

This results in an error "The 'Microsoft.ACE.OLEDB.12.0' provider is not registered on the local machine."

When I copy the same code into a c# console application it works fine. I am running Windows 7 64-bit and 32-bit Office 2007 excel. In the Build properties the platform is set to "Any CPU". In the WCF project the 32-bit preferred is unchecked and greyed out but in the Console application it is ticked. I have tried downloading Microsoft Access Database Engine 2010 Redistributable , but this has not helped.

If I change the Platform target to X86 then I get the following runtime error:

WcfSvcHost encountered a critical error and must exit. This may be caused by invalid configuration file. Please inspect additional information below for detail.

System.BadImageFormatException: Could not load file or assembly 'file:///C:\Users\User\documents\visual studio 2013\Projects\DCRules2\DCRules2\bin\Debug\DCRules2.dll' or one of its dependencies. An attempt was made to load a program with an incorrect format.

Has any one come across this before and more importantly does anyone have a fix ?


The Excel file cannot be 32-bit or 64-bit (document is document), but Microsoft.ACE could be. Just for an experiment, you can always compile your application to x86 target: Project Properties -> "Build" tab -> "Platform target" list box. The x86 instruction-set architecture is compatible with two other (64-bit) architectures and is supported on 64-bit versions of Windows via WoW64 ([^]). I don't believe the problem is there; you rather need to check up your code. Please see these threads:[^],[^].

One good alternative is using Open XML SDK instead. Please see my past answers referenced from this one: How to add microsoft excel 15.0 object library from Add Reference in MS Visual Studio 2010[^].

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Hi Sergey,
if you look at my original post you will see that I already set PLatform Target to X86 but this resulted in the run time error that I also posted.

As per example , why can I run code in Console application successfully but am unable to run identical code in WCF application ?

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