I can't figure out why I am getting a "DataTable already belongs to another DataSet" exception.
Here is my code:
DataSet AlertSet = new DataSet();
DataTable generalAlertData = new DataTable("GeneralAlertData");
generalAlertData = //function that returns datatable
//throws exception
AlertSet.Tables.Add(generalAlertData)
When is another dataset being created and when is the generalAlertData datatable being added to it?
I tried using a slightly different syntax to create and add the table and got the same error:
DataSet AlertSet = new DataSet();
DataTable generalAlertData = //function that returns datatable
//throws exception
AlertSet .Tables.Add(generalAlertData);
It depends on what your function that retrieve the datatable does.
If that function use a DataAdapter and fills a dataset then you have the DataSet property of the table automatically assigned and you need to remove it before assigning a different DataSet
You could try this to remove the original DataSet and use your own
DataTable generalAlertData = GetTable();
DataSet u = generalAlertData.DataSet;
u.Tables.Remove(generalAlertData.TableName);
AlertSet.Tables.Add(generalAlertData);
So, if your hypothetical GetTable works in this way
public DataTable GetTable()
{
...
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
return ds.Tables[0];
}
then you have the DataSet assigned to the returned datatable.
Instead this code doesn't assign anything to the DataSet property
public DataTable GetTable()
{
...
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
return dt;
}
The DataTable returned from the method call, was added to a DataSet. Make sure it's not added to a DataSet; just build a stand alone DataTable.
As a side-note, returning a DataTable from a method call that assigns to this one makes the line above it irrelevant (the new).
This is an old question now but maybe this answer will help others.
I too received this error. I looked through my source code, found literally no other datasets and was puzzled as to why this was happening.
The solution to my issue was in my data access library. It didn't have a "getDataTable" routine but I did have a getDataset routine. When I needed just a datatable I called getDataset and took the tables(0) datatable instance.
The end result of this is that I got back my datatable like I wanted, but the datatable was already part of the dataset returned from my data access call. Thus, the error.
I had to add a getDatatable routine into my data access library to eliminate this problem.
I had the same problem and I solved it using Remove. In my opinion, your code could be this:
DataSet AlertSet = new DataSet();
DataTable generalAlertData = new DataTable("GeneralAlertData");
AlertSet.Tables.Add(generalAlertData);
AlertSet.Tables.Remove(generalAlertData);
Please, let me know if this code works.
My working code was like this:
DataTable myTable = new DataTable();
private void Save()
{
DataSet myDataSet = new DataSet();
myDataSet.Tables.Add(myTable);
myDataSet.Tables.Remove(myTable);//This works
myDataSet.WriteXml("myTable.xml");
}
private void buttonSave_Click(object sender, EventArgs e)
{
Save();
}
Every time I clicked the button buttonSave, the message “DataTable already belongs to another DataSet" appeared. After writing the line code myDataSet.Tables.Remove(myTable);//This works the application started running without problems and now I can click the button more times, without losing the value of myTable and without the error message.
I hope this can help.
Related
I assigned a table data in dataset to a new table. When I clear the new table(dt), table(ds.Tables[0]) in dataset has been cleared too, why? And how to avoid it to be cleared too?
DataTable dt = new DataTable();
DataSet ds = new DataSet();
\\some code to assign data to ds
below code will execute when a button is clicked, first click works well,second click caused table[0] in ds empty
dt.Clear()
dt = ds.Tables[0];
Change:
dt = ds.Tables[0];
to:
dt = ds.Tables[0].Copy();
This way, dt will hold a copy of dt.Tables[0], rather than a reference to the same underlying DataTable
I am trying to clone Datable from one dataset to datatable from other Dataset, but it does not work.
Dataset ds = new Dataset();
ds.Tables.Add("key");
ds.Table["key"] = cust.Tables[0].Clone(); // This line is not working
Above code gives below error
Property or indexer 'System.Data.DataTableCollection.this[int]' cannot be assigned to — it's read only
cust is also a Dataset. Can someone help me resolve this
The error you are getting is similar to this:
Property or indexer 'System.Data.DataTableCollection.this[int]' cannot
be assigned to -- it is read only
You are doing it right once, and then you are doing it wrong in the line after.
The error is telling you, that cust.Tables[0] is read only. You cannot assign any values to it, so you have to use the Add() method:
DataSet cust = new DataSet(); // create source DataSet
cust.Tables.Add("sourceTable"); //add table to source
DataSet ds = new DataSet(); // create target DataSet
ds.Tables.Add((cust.Tables[0]).Clone()); //clone source table
(ds.Tables[0]).TableName = "keys"; // assign name
You need to wrap ds.Tables[indexer] in paranthesis () so the compiler treats it as a datatable.
You should assign a DataTable variable to keep the readability:
var sourceTable = cust.Tables[0];
/* ... */
ds.Tables.Add(sourceTable.Clone());
I've found some solutions on stackoverflow and other sites like this (assume the connection is already opened):
sc.Open();
DataSet ds = new DataSet();
MySqlDataAdapter adapter = new MySqlDataAdapter("select * from mydatabase.mytable;", sc);
adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
adapter.Fill(ds);
dataGridView1.DataSource = ds;
sc.Close();
but it's not working propoerly. All I get is an empty datagridview which let's me assume that the data is not loaded.
When I first loaded the data to a list - list myList with MySQLDataReader, I could load the data normally to the datagridview with the following code:
foreach (myClass a in myList)
{
this.dataGridView1.Rows.Add(a.Id, a.2ndColumn, a.3rdCoulmn, and so on..;
}
Can you please tell me why I couldn't load the datatable with the MySQLAdapter? Some of the asnwers I checked showed I should be able to load it and display it this way..
You should take a look at this link, I've used it a while ago and it worked fine for me.
Also, the for loop you have isn't needed, when linking an collection to the DataSource property it should automatically update the GridView.
I have a dataset containing some datatables, now i want to fetch a datatable from db and add it to the existing datatable in dataset i am using below line
return (DataSets.General.StudentDataTable) ds.Tables["DSDummy"];
But its giving me following error
Cannot implicitly convert type 'System.Data.DataTable' to
DataSets.General.StudentDataTable'. An explicit conversion exists
can someone please tell me how to cast this object? any help would be appreciated
Thanks
If ds is a strongly typed dataset, I would expect it to have an explicit property for the DSDummy table, something like ds.DSDummy, rather than going through the Tables collection, which bypasses the strong typing.
However, even as it stands, the explicit cast should have worked. Is it possible that you have DataSets.General.StudentDataTable defined more than once - once manually and once automatically from the DataSet Generator - and it's conflicting?
If you're trying to load one DataTable into another one, you can use the DataTable.Merge method:
DataSets.General.StudentDataTable.Merge(ds.Tables["DSDummy"]);
Check out the MSDN documentation
Below code was taken from the above link.
DataSet customerOrders = new DataSet("CustomerOrders");
DataTable ordersTable = customerOrders.Tables.Add("Orders");
DataColumn pkOrderID =
ordersTable.Columns.Add("OrderID", typeof(Int32));
ordersTable.Columns.Add("OrderQuantity", typeof(Int32));
ordersTable.Columns.Add("CompanyName", typeof(string));
ordersTable.PrimaryKey = new DataColumn[] { pkOrderID };
Try like below... may be it help you...
If you want to return dataset and assign to a Dataset then follow the below method..
DataSet ds = new DataSet();
ds = GetData();
public dataset Sample GetData()
{
......
.......
return ds
}
If you want to return Datatable and assign that to Dataset then follow the below method.
DataSet ds = new DataSet();
ds.Tables.Add(GetData());
public datatable Sample GetData()
{
......
.......
return ds.Tables["DSDummy"];
}
Im trying to retrieve a datatable that I put into a session variable, however when i do it apears that there are no columns...
I have done this before in VB.NET, I'n now using C#, and it worked perfectly, and as far as i can see there is no change in the code other than the obvious syntax changes.
EDIT:
The dt (in part 2) variable has the right data when i look in the data visulization window, but i have noticed that the other properties associated with a datatable are abscent. When i hover over a normal looking datatable with my mouse it looks like the following: " dt ----- {System.Data.DataTable}" but in the class im working on it just looks like "dt ----- {}". Also, after I return the session variable into the dt I clone it (dtclone = dt.clone(); ) and the clone is empty in the data visulizer.... what on earth!
EDIT 2:
I have now also tried converting the first datatable to a dataset, putting this in the session variable, and recoverting it back to a datatable in the class.
Am starting to wonder if it is a probelm with:
dt.Load(sqlReader);
The data does appear after this step though in the dataset visualiser, but not after being cloned.
Code below.
All help very welcome!
Thanks in advance
Chris
1) SQL command in a webhandler, the results of which populate the datatable to be put into the session variable.
DataTable dt = new DataTable();
SqlDataReader sqlReader= default(SqlDataReader);
SqlDataAdapter sqlAdapter = new SqlDataAdapter();
sqlReader = storedProc.ExecuteReader(CommandBehavior.CloseConnection);
dt.Load(sqlReader);
System.Web.HttpContext.Current.Session["ResultsTable"] = dt;
2) Part of the code in a class which performs calculations on the table:
DataTable dt = (DataTable)HttpContext.Current.Session["ResultsTable"];
did you call DataTable dispose after setting Session Var?
Because if you do this, solution is like this:
System.Web.HttpContext.Current.Session["ResultsTable"] = dt.Copy();