LinqConnect Professional Version 4.2.222 (04-Apr-2013) - One Model with many DataBase

[AKRRKA]

The problem is as follows:
Need to make an application that will transparently work with multiple databases (eg MySQL, Oracle, SQLite). I bought already and try to use this "LinqConnect Professional 4.x".

The question is:
How to do it. It is desirable that had one "DataContext", ie in the project one ORM model and could be through it gain access to any of the databases to which the user wishes to connect.

There is an example of such a realization and is it possible at all?
Very much I ask greetings to this example.

[MariiaI]

To use the same DataContext and entity classes for different databases, you should provide different mapping information for the context instances. For example, you can do this via the XML mapping.

In this case you should do the following:
1. Change "Mapping Mode" in model settings to "File". Entity Developer will generate the mapping file ([YourModelName].xml) for the database you are using.
2. Make a copy of the generated xml file.
3. Change connection in the Database Explorer to the necessary one.
4. Check the Target Server in Model Settings -> Synchronization -> Mapping. It must be set to the one that you are going to use (i.e., to MySQL Server of the proper version).
5. Run the Update Database Wizard to create the database objects; select the 'Regenerate Storage' option at the first step of the wizard.
6. Save changes and open the mapping file. Now it should contain mapping for the new database.
7. Save this new mapping file somewhere and repeat the previous steps for other databases, if necessary.

For more information about using XML mapping, see http://www.devart.com/linqconnect/docs/POCO.html

[AKRRKA]

Thanks. But...
Can you give as examples a small application.

[MariiaI]

We have sent you a sample project, that demonstrates how to work with multiple databases using one DataContext. Please check that the letter is not blocked by your mail filter.

[AKRRKA]

Thank you so much!

Best regards,
Karen Arzumanyan

[AKRRKA]

Hello.

I have new big problem.

I create my application like in you sample.
All OK, but if I need change DB type without close/open application, i get a problem.
You can see this error in my example.

1) Connect to MySQL (automated get data and show in grid);
2) Disconnect Context connection and dispose contest, and context variable assign null;

Code: Select all

        private void sbCloseConnection_Click(object sender, EventArgs e)
        {
            DataContext.Connection.Close();
            DataContext.Dispose();
            DataContext = null;
        }

3) Connect to SQL Server. And get Error!
The connection is open correctly. But if I try get data have the error -2146233088

If first connect to SQLServer, and after to MySQL, also get tis error.

What am I doing wrong?How to correctly remove and reset the variable context to use it for other databases?

Sample application: http://rghost.ru/45031534

PS: It is very important to me. Please help a high-priority issue.
PPS: Use LinqConnect Professional Version 4.1.197 (28-Feb-2013).

Thanks.

[MariiaI]

When working with different DBMSs it is necessary to clear the "Preserve schema name in storage" check box in the Model Settings. The error, you are getting, occurs because your generated xml files contain the information, like this

Code: Select all

 <Table Name="dbo.Users" Member="Users">

but should be like this

Code: Select all

<Table Name="Users" Member="Users">

Thus, please do the following:
- clear the "Preserve schema name in storage" check box in the Model Settings;
- re-create your model in order to changes become effective for all Entity classes; use the "Update Model from Database" wizard with the selected "Recreate Model" option;
- re-generate xml mapping files for the necessary databases.

Please tell us if this helps.

[AKRRKA]

Yes, for DataGridView, this solution worked.

But in fact I used in the project DevExpress.XtraGrid. And with it the solution did not work.
Also i have a problem without any grid, just select data after change database.

First problem:
1) Connect MySQL;
2) Press - "Get Xtra";
3) Connect SQL Server;
4) Press - "Get Xtra" - Have a Error;
If first connect to SQLServer, and after to MySQL, also get tis error on step 4.
Code for "Get Xtra":

Code: Select all

var rllist = from us in DataContext.Users select us;

var iCount = rllist.Count();
MessageBox.Show(@"Get Count : " + iCount.ToString());

gridControlData.DataSource = null;
gridControlData.DataMember = null;
gridControlData.DataBindings.Clear();

MessageBox.Show(@"Select Data - for DevExpress.XtraGrid");
gridControlData.DataSource = rllist;
gridControlData.RefreshDataSource();

Second problem:
1) Connect MySQL;
2) Press - "Get Error";
3) Connect SQL Server;
4) Press - "Get Error";
If first connect to SQLServer, and after to MySQL, also get tis error on step 4.
Code for "Get Error":

Code: Select all

var isNotEmpty = DataContext.Users.Any(ug => ug.Name != "");
MessageBox.Show(@"isNotEmpty : " + isNotEmpty.ToString());

Please help me.

This sample show two error (all referenced DevExpress components included).
WindowsFormsApplication8.rar

PS: Use LinqConnect Professional Version 4.2.222 (04-Apr-2013);

[MariiaI]

Thank you for the test sample.
We couldn't reproduce the first issue with your sample (with the DevExpress gridview). Please specify the full text of the exception and its stack trace.
As for the second issue, we have reproduced it. We will investigate it and inform you about the results as soon as possible.

[AKRRKA]

OK. Tomorrow I will provide the details on the first problem.

[AKRRKA]

Video with demonstration first problem: Link
Get different error text for the cases when first connecting to MySQL and if the first server to the SQL Server. You can look at the video.

I think that both problems are related. But I can not understand how. Cause I reset (dispose and assign to null) context variables. But still is stored somewhere previous provider.

[MariiaI]

Thank you for the additional information. Apparently, these issues are related to the query cache. We have made some changes which should fix them. We will inform you when the new build with the fix is available for download.

[AKRRKA]

Thank you. For me this is very important.
Really looking forward the corrected version.

[MariiaI]

The new build of LinqConnect 4.2.229 is available for download now. It can be downloaded from http://www.devart.com/linqconnect/download.html (trial version) or from Registered Users' Area (for users with valid subscription only).
For more information please refer to http://forums.devart.com/viewtopic.php?f=31&t=26911

[AKRRKA]

Thanks!
I tested LinqConnect Professional Version 4.2.229 (18-Apr-2013), and all work without error.