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Database not updating when using DataSet

I am doing a small project to learn how to use DataSet but i have a small problem. Consider following code:
foreach (DatabaseDataSet.ApplicationRow rowApplication in database.Application)
{
if (rowApplication.AID.ToString() == lblIDApplication.Text)
{
rowApplication.Date= tbApplicationDatum.Text;
rowApplication.Status = tbApplicationStatus.Text;
applicationAdapter.Update(rowApplication);
break;
}
}
I don't know why but the database doesn't get updated. The DataRow is being updated as when I call the data again I see the new value. But when I re-run my application it's back to it's old value again. Any help?
EDIT: I'm working with strongly typed DataSet

You need to call the Update method of your adapter to propogate the changes
AcceptChanges only updates the changes in memory for the row and does not migrate those to the database
MSDN
AcceptChanges and RejectChanges only apply to DataRow related changes
(that is, Add, Remove, Delete, and Modify). They are not applicable to
schema or structural changes.
Calling AcceptChanges will not replicate these changes back to the
data source if the DataSet was filled using a DataAdapter. In that
situation, call Update instead
See Updating Data Sources with DataAdapters for more information

Its important to remember that the DataSet is a 'local copy' of the data not a 'live link' to the DB. If your DataSet is populated by a IDataAdaptor (say a TableAdaptor) for example you need to call the DataAdaptors Update method passing in the Updated dataset to sync the results back to the underlying DB.
Also I would suspect you DONT want to be doing 'new ApplicationTableAdapter()' because typically you would want to update with the TableAdaptor you populated with, at the least you would need to ensure you had the correct connection, query etc set up.

SOLUTION: It happens that nothing was wrong with the code. I had two ConnectionString defined in App.config. I forgot to remove the first one after I removed a previous database that had errors in it. Upon removing the first ConnectionString, everything worked.

Using a BindingSource to link a DataSet to a DataGridView, but there's no data

This is my first time working with DataSets and BindingSources, so please be gentle on me.
As part of a more complicated reporting system (I've distilled it down to a basic incarnation, but it still won't run correctly), I'm trying to pull data from a database using a DataSet problematically (that is, not set up via the designer). Here is the code I have so far:
// pull the data set
var dsReportData = new Reports2.ReportTest2();
dsReportData.BeginInit();
dsReportData.SchemaSerializationMode = SchemaSerializationMode.IncludeSchema;
// bind tha data set
BindingSource bsReportBinding = new BindingSource();
((ISupportInitialize)bsReportBinding).BeginInit();
bsReportBinding.DataMember = dsReportData.Tables[0].TableName;
bsReportBinding.DataSource = dsReportData;
bsReportBinding.ResetBindings(true);
// test this stuff
dgvTester.DataSource = bsReportBinding;
dsReportData.EndInit();
((ISupportInitialize)bsReportBinding).EndInit();
I based this on the code I saw in a .designer.cs file after setting up binding through the designer. dgvTester is just a DataGridView with the default properties created in the designer.
The ReportTest2 dataset has just one TableAdapter in it, added via designer.
Now, if I went to Data -> Preview Data in VS and previewed the ReportTest2.payments.Fill,GetData () object, it returns data just fine, same as if I ran the query I used to crate the TableAdapter in SQL Server Management Studio.
However, running the actual code results in the DataGridView getting the column names from the query result, but not the actual data. The debugger reveals that dsReportData.payments.Rows.Count == 0 (and that, yes, dsReportData.Tables[0] is payments).
I ultimately intend to use the BindingSource to provide data to a ReportViewer, but first things first is making sure there's no problems with retrieving the data before going onto debug the report.
Hopefully I'm missing something obvious here. I hope so...

Figured it out after some trial and error. This is the part I was missing:
var TableAdapter = new Reports2.ReportTest2TableAdapters.paymentsTableAdapter();
TableAdapter.Fill(dsReportData.payments);
I didn't see it in the code I was referencing because the designer snuck it into the .cs file instead of the .designer.cs file. This made the data appear.

A DataTable named 'Table' already belongs to this DataSet

when i am adding second table(dtResult) to data set that time it's giving error
A DataTable named 'Table' already belongs to this DataSet.
DataTable dtSession = new DataTable();
DataTable dtResult= new DataTable();
dtResult.TableName = "A";
dtSession.TableName = "B";
dtSession = objOpt.GetSearchDetails().Copy();
ds.Tables.Add(dtSession);
dtResult = objOpt.Search_Synchronous().Copy();
ds.Tables.Add(dtResult);
Thanks in advance

You need to name the tables after getting the copy from your method and before adding it to the DataSet.
DataTable dtResult= new DataTable();
dtSession = objOpt.GetSearchDetails().Copy();
dtSession.TableName = "B";
ds.Tables.Add(dtSession);
dtResult = objOpt.Search_Synchronous().Copy();
dtResult.TableName = "A";
ds.Tables.Add(dtResult);
Since you are getting the copy from your methods objOpt.GetSearchDetails().Copy() and objOpt.Search_Synchronous().Copy(), they are overwriting the names assigned to the table previously, and both of these are returning the table with name Table, that is why you are getting this error

I was getting this exception today, but it had nothing to do with adding a DataTable.
I have an ASP.Net Core WebApi, and in the Post and Put endpoints, I was attempting to save/update the new record and also search in the database (in the same table) for an existing record with the same details, and if such a record exists, to update it.
I was getting that exception when it tried to save these changes.
The solution was to split it up, save the new/updated record first...
// Avoid an "A DataTable named 'Users' already belongs to this DataSet." exception
await _context.SaveChangesAsync();
... and then check for an existing record, update it if necessary, and then doing a separate save...
await _context.SaveChangesAsync();
Yup, it's weird, but saving twice fixed this issue for me.
(I appreciate that this doesn't answer this exact StackOverflow question, but for anyone stumbling onto this page when they hit this strangely-worded exception, this'll be a lifesaver !)

I received this error when running command.ExecuteDataSet on a stored procedure where I declared a table variable then queried that table multiple times to return several datatables in the dataset. Because each datatable was queried from the same table, they all had the same name '#t'. I was able to resolve it by creating multiple table variables with different names in the stored procedure.

Need easy way out for change detection in dataset programatically c#

what is the easiest way to find out those data which has been changed in dataset. i need point out programatically those data which has been modified.

DataSet changes = ds.GetChanges();
This will return a dataset with all the changes since the last time Accept or reject was called on the dataset.
You can also apply rowstatefilters i.e. if you want to see only those rows that have been modified:
DataSet changes = ds.GetChanges(DataRowState.Modified);
Or Added:
DataSet changes = ds.GetChanges(DataRowState.Added);

You can use GetChanges method on the DataSet object as described at : http://msdn.microsoft.com/en-us/library/a4ey25we.aspx

.Net Simple Data File usage

I've created a new project in .Net (2010 4.0) and added an SDF data file. I've generated a dataset and created a table in it (and I believe generated the Fill and other methods).
In code, I'm trying to add a row to the database.
eBureauScrubber.App_Data.matchingtempDataSet ds = new App_Data.matchingtempDataSet();
eBureauScrubber.App_Data.matchingtempDataSet.ctfFileRow row = ds.ctfFile.NewctfFileRow();
row.Address = "123 Main St.";
row.City = "Overland Park";
row.FirstName = "Matt";
row.LastName = "Dawdy";
row.rownum = 1;
EDIT: Added the next bit of code.
ds.ctfFile.Rows.Add(row);
ds.ctfFile.AcceptChanges();
ds.AcceptChanges();
eBureauScrubber.App_Data.matchingtempDataSetTableAdapters.ctfFileTableAdapter ctfa = new App_Data.matchingtempDataSetTableAdapters.ctfFileTableAdapter();
ctfa.Update(ds.ctfFile);
This runs fine. However, after the program completes, the data is not persisted in the database. What am I missing?
EDIT: I've tried all different combinations of AcceptChanges() on the datatable, the dataset, running update() before, after, etc. I'm missing something huge here. I'm not even sure it is connecting to the "right" database. Maybe that's my problem.
EDIT 2: Here's what I did to get this to work (it's still funky, though).
Change the properties of my DB file in App_Data to "Do Not Copy"
Manually copy that db file to bin\debug\app_data
Use the data adapter's fill method to fill the ds.ctfFile data table.
Create a row (.NewctfFileRow())
Set values on that row.
ds.ctfFile.Rows.Add(row)
ds.ctfFile.AcceptChanges();
ds.AcceptChanges();
Call the adapater's update method.
Now, the data is in my database file (in bin\debug\app_data), but I can't see it because the Data Sources connection. I'm still trying to find out how to do that.

It should have generated a TableAdapter class with a .Update() method that you have to call to save data in your database. See MSDN for some examples.