try to load .Net dll in MATLAB

I have tried to load a .Net dll in MATLAB and i have got the following error message: " Could not load file or assembly 'file:///C:\....' or one of its dependencies. An attempt was made to load a program with an incorrect format. Source: mscorlib" The dll has built on the same pc. I use x64 softwares and Win 7. Has anyone solution for this problem? Thanks

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the version of MATLAB is 2011b