Working with MSI Databases

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Querying a database

    using (Database db = new Database("product.msi", DatabaseOpenMode.ReadOnly))
-    {
-        string value = (string) db.ExecuteScalar(
-            "SELECT `Value` FROM `Property` WHERE `Property` = '{0}'", propName);
-    }

1. Create a new Database - instance referring to the location of the .msi or .msm file.

2. Execute the query:

The ExecuteScalar - method is a shortcut for opening a view, executing the view, and fetching a single value.
The ExecuteQuery - method is a shortcut for opening a view, executing the view, and fetching all values.
Or do it all manually with Database.OpenView, - View.Execute, and - View.Fetch.

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Updating a binary

    Database db = null;
-    View view = null;
-    Record rec = null;
-    try
-    {
-        db = new Database("product.msi", DatabaseOpenMode.Direct);
-        view = db.OpenView("UPDATE `Binary` SET `Data` = ? WHERE `Name` = '{0}'", binName))
-        rec = new Record(1);
-        rec.SetStream(1, binFile);
-        view.Execute(rec);
-        db.Commit();
-    }
-    finally
-    {
-        if (rec != null) rec.Close();
-        if (view != null) view.Close();
-        if (db != null) db.Close();
-    }

1. Create a new Database - instance referring to the location of the .msi or .msm file.

2. Open a view by calling one of the Database.OpenView overloads.

Parameters can be substituted in the SQL string using the String.Format syntax.

3. Create a record with one field containing the new binary value.

4. Execute the view by calling one of the View.Execute overloads.

A record can be supplied for substitution of field tokens (?) in the query.

5. Commit the Database.

6. Close the handles.

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About handles

Handle objects (Database, View, Record, SummaryInfo, Session) will remain open until - they are explicitly closed or until the objects are collected by the GC. So for the tightest - code, handle objects should be explicitly closed when they are no longer needed, - since closing them can release significant resources, and too many unnecessary - open handles can degrade performance. This is especially important within a loop - construct: for example when iterating over all the Records in a table, it is much cleaner - and faster to close each Record after it is used.

The handle classes in the managed library all extend the - InstallerHandle - class, which implements the IDisposable interface. This makes them easily managed with C#'s - using statement. Alternatively, they can be closed in a finally block.

As a general rule, methods in the library return new handle objects that should be managed - and closed by the calling code, while properties only return a reference to a prexisting handle - object.

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See also:

MSI Diff Sample Tool
Database Class

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