For ArcGIS Mobile, the deployment instructions are not complete. The help page for Deploying ArcGIS Mobile Application does not talk about where to place .dll(s).
This issue is not reproducible in the current release of the software. If you are encountering this issue, please contact Esri Technical Support (for customers in the United States) or your Esri distributor (for customers outside the United States) to resolve this issue.
解决办法
Following are the set of instructions from the forum to place the dlls in the different folders -In 9.3 deployment for ArcGISMobile SDK has changed. You are no longer required to deploy dll(s) to app folder. The managed assembly is now in GAC and all native dll(s) should be located under \ArcGIS\Bin. You also need to deploy a reg key to tell where to find the native dll(s).For example, the following registry key should be created \Local Machine\Software\ESRI\ArcGIS and set InstallDir=C:\Program Files\ArcGIS\InstallDir is key value name and value data is set to C:\Program Files\ArcGIS.The followings summarize where the files should go.1. ESRI.ArcGIS.Mobile.dll should be deployed to GAC2. ESRIMobileCore.dll should go in to \Program Files\ArcGIS\Bin3. ESRIMobilePE.dll should go in to \Program Files\ArcGIS\Bin4. ESRIMobileSdc.dll should go in to \Program Files\ArcGIS\BinTo gac ESRI.ArcGIS.Mobile.dll you can use gacutil to do it. The example provided in code gallery is a setup project which will do GAC and install reg key and the dll(s) for you.