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Posted 20 Jul 2004

Compact and Repair Access Database using C# and late binding

, 20 Jul 2004
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The code compacts and repairs an MS Access database from C# code using a JRO.JetEngine COM-object. Binding occurs at runtime, no references, no interops. Pure System.Reflection.


This code compacts and repairs an MS Access database from a C# .NET application, no matter if it's a simple ".mdb", or a ".mdw"-secured workgroup-shared DB. It performs exactly the same operation as "Tools - Database Utils - Compact and Repair Database..." menu item in the MS Access application. The code uses "late binding" (creating COM-objects in memory at runtime), and that's why you don't need any annoying interop COM references in your project. You don't even need MS Office installed. Just make sure you have a Jet Engine (Jet is included in MDAC package, which comes with any Windows installation starting from NT 4).


Don't you hate COM-library references in .NET-projects? I believe that pure .NET-code has to be free of any interops, RCWs, and other referenced COM-stuff. Basically because there's a load of different versions of MS libraries (for example, MS Office Object Library 9, 10, 11 etc.). We never know what version of MS Office is installed on a client machine, that's why we should access a COM-object via ProgID, and not CLSID. For example: you want to be sure, that when you call for an "Excel.Application", you get Excel, no matter what version of MS Office is installed. And when you add a reference "MS Excel 10 Object library", you add a strong limitation to your software! So... use System.Reflection and late binding.

Using the code

Just call a method CompactAccessDB. This method compacts and repairs your database.


  • connectionString - connection string to your database.
  • mdwfilename - is a full name (path+name) of an MDB-file you want to compact and repair.

Due to Jet limitations, the method compacts your database to a new file, so we have to copy the new compacted file over an old one.

When you call this method, make sure that there's no open connections to your database. Stop your threads.

Now, to the code:

/// <summary>
/// MBD compact method (c) 2004 Alexander Youmashev
/// !make sure there's no open connections
///    to your db before calling this method!
/// </summary>
/// <param name="connectionString">connection string to your db</param>
/// <param name="mdwfilename">FULL name
///     of an MDB file you want to compress.</param>
public static void CompactAccessDB(string connectionString, string mdwfilename)
    object[] oParams;

    //create an inctance of a Jet Replication Object
    object objJRO = 

    //filling Parameters array
    //cnahge "Jet OLEDB:Engine Type=5" to an appropriate value
    // or leave it as is if you db is JET4X format (access 2000,2002)
    //(yes, jetengine5 is for JET4X, no misprint here)
    oParams = new object[] {
        "Provider=Microsoft.Jet.OLEDB.4.0;Data" + 
        " Source=C:\\tempdb.mdb;Jet OLEDB:Engine Type=5"};

    //invoke a CompactDatabase method of a JRO object
    //pass Parameters array

    //database is compacted now
    //to a new file C:\\tempdb.mdw
    //let's copy it over an old one and delete it

    System.IO.File.Move("C:\\tempdb.mdb", mdwfilename);

    //clean up (just in case)

Points of Interest

Interesting, that Jet Engine 5 is used for JET4X databases. Be careful. See the table:

Jet OLEDB:Engine TypeJet x.x Format MDB Files


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Alexander Yumashev
Founder Jitbit
Russian Federation Russian Federation
I'm CEO/Founder and lead developer at Jitbit Software. My personal blog is here

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Comments and Discussions

QuestionWorking Example Pin
Grunf167-Jan-16 3:35
memberGrunf167-Jan-16 3:35 
AnswerRe: Working Example Pin
Wendell D H7-Jan-16 4:37
professionalWendell D H7-Jan-16 4:37 
GeneralRe: Working Example Pin
Grunf1629-Jan-16 11:46
memberGrunf1629-Jan-16 11:46 
SuggestionAccess recovery tool Pin
Member 1172274727-May-15 3:04
memberMember 1172274727-May-15 3:04 
QuestionIs this compaction code for access public domain or what license Pin
Member 45854253-Sep-14 4:21
memberMember 45854253-Sep-14 4:21 
Questioni had error using this code so i used Pin
yakirmanor5-Dec-13 1:45
memberyakirmanor5-Dec-13 1:45 
QuestionError Pin
RogueX2010-Jul-13 7:17
memberRogueX2010-Jul-13 7:17 
AnswerRe: Error Pin
RogueX2010-Jul-13 15:07
memberRogueX2010-Jul-13 15:07 
GeneralMy vote of 5 Pin
StewBob18-Jul-12 5:17
memberStewBob18-Jul-12 5:17 
QuestionError when I run this Code Pin
Pooja N Khanapurkar20-Mar-12 4:41
memberPooja N Khanapurkar20-Mar-12 4:41 
QuestionCompact and Repair Pin
lkn_o20-Mar-12 2:43
memberlkn_o20-Mar-12 2:43 
GeneralMy vote of 5 Pin
kozura18-Feb-11 0:37
memberkozura18-Feb-11 0:37 
GeneralCreate,Compact/Compress and Convert MDB database using ASP/VBScript Pin
elizas11-Feb-10 23:21
groupelizas11-Feb-10 23:21 
GeneralCreate,Compact/Compress and Convert MDB database using ASP/VBScript Pin
elizas3-Feb-10 1:04
groupelizas3-Feb-10 1:04 
GeneralReally useful Pin
Alexander Stankov20-Sep-09 22:57
memberAlexander Stankov20-Sep-09 22:57 
QuestionCan it run on Windows 7? Pin
tiendungdl13-Sep-09 18:29
membertiendungdl13-Sep-09 18:29 
AnswerRe: Can it run on Windows 7? Pin
John Reiter11-Oct-12 15:02
memberJohn Reiter11-Oct-12 15:02 
QuestionInstance of type object ? Pin
Stuard25-Aug-09 15:12
memberStuard25-Aug-09 15:12 
GeneralIt's Not Compacting or repairing MS access database properly.. Pin
Raj N Verma11-Aug-09 0:00
memberRaj N Verma11-Aug-09 0:00 
GeneralEach iteration increases the size of my Access 97 MDB Pin
MerrimackBobNH27-Jun-09 8:23
memberMerrimackBobNH27-Jun-09 8:23 
GeneralြGreat Pin
Aung Sithu2-Apr-08 16:02
memberAung Sithu2-Apr-08 16:02 
QuestionException has been thrown by the target of an invocation. Pin
Member 26460376-Mar-08 22:11
memberMember 26460376-Mar-08 22:11 
GeneralVery helpful. Thx. Pin
David Catriel27-Nov-07 17:57
memberDavid Catriel27-Nov-07 17:57 
Generalthanks [modified] Pin
M.S. Babaei16-Nov-07 23:24
memberM.S. Babaei16-Nov-07 23:24 
GeneralWarning Pin
Tom McAnnally15-Apr-07 14:04
memberTom McAnnally15-Apr-07 14:04 

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