What I'm trying to do with the code is to export a dataset to XML.
This is what I'm currently using:
dataSet.WriteXml(fileDialog.FileName, XmlWriteMode.WriteSchema);
My dataSet is a typed dataset properly formed (by this I mean, all tables have PK, and FK relations are set between all existing tables in the dataSet). Some relationships are nested relationships. The table "TABLE" has two FK and at the same time is parent to other 8 tables.
I get the following error: "Cannot proceed with serializing DataTable 'TABLE'. It contains a DataRow which has multiple parent rows on the same Foreign Key."
Cna anyone give me some pointers on what I'm doing wrong? and why I'm getting this error message?
Thanks in advance.
I know it's a bit late, but I have found a workaround.
I ran into the same problem while trying to read a schema into a dataset that has the relations. The error you will get in that case is:
'The same table '{0}' cannot be the child table in two nested relations'
I will share what I have learned
The dataset operates in two modes, though you CAN NOT tell this from the outside.
(a) I'm a strict/manually created dataset, don't like nested relations
(b) I'm a container for a serialized object, everything goes.
The dataset you have created is currently an 'a', we want to make it a 'b'.
Which mode it operates in is decided when a DatSet is 'loaded' (xml) and or some other considerations.
I spend feverish hours reading the code of the DataSet to figure out a way to fool it, and I found that MS can fix the problem with just the addition of a property on the dataset and a few additional checks. Checkout the source code for the DataRelation: http://referencesource.microsoft.com/#System.Data/System/Data/DataRelation.cs,d2d504fafd36cd26,references and that the only method we need to fool is the 'ValidateMultipleNestedRelations' method.)
The trick is to fool the dataset into thinking it build all relationships itself. The only way I found to do that is to actually make the dataset create them, by using serialization.
(We are using this solution in the part of oursystem where we're creating output with a DataSet oriented 3rd party product.)
In meta, what you want to do is:
Create your dataset in code, including relationships. Try if you
can mimic the MS naming convention (though not sure if required)
Serialize your dataset (best to have not any rows in it)
Make the serialized dataset look like MS serialized it. (I'll
expand on this below)
Read the modified dataset into a new instance.
Now you can import your rows, MS does not check the relationships,
and things should work.
Some experimentation taught me that in this situation, less is more.
If a DataSet reads a schema, and finds NO relationships or Key-Columns, it will operate in mode 'b' otherwise it will work in mode 'a'.
It COULD be possible that we can still get a 'b' mode dataset with SOME relationships or Key-Columns, but this was not pertinent for our problem.
So, here we go, this code assumes you have an extension method 'Serialize' that knows how to handle a dataset.
Assume sourceDataSet is the DataSet with the schema only.
Target will be the actually usable dataset:
var sourceDataSet = new DataSet();
var source = sourceDataSet.Serialize();
// todo: create the structure of your dataset.
var endTagKeyColumn = " msdata:AutoIncrement=\"true\" type=\"xs:int\" msdata:AllowDBNull=\"false\" use=\"prohibited\" /";
var endTagKeyColumnLength = endTagKeyColumn.Length - 1;
var startTagConstraint = "<xs:unique ";
var endTagConstraint = "</xs:unique>";
var endTagConstraintLength = endTagConstraint.Length - 1;
var cleanedUp = new StringBuilder();
var subStringStart = 0;
var subStringEnd = source.IndexOf(endTagKeyColumn);
while (subStringEnd > 0)
{
// throw away unused key columns.
while (source[subStringEnd] != '<') subStringEnd--;
if (subStringEnd - subStringStart > 5)
{
cleanedUp.Append(source.Substring(subStringStart, subStringEnd - subStringStart));
}
subStringStart = source.IndexOf('>', subStringEnd + endTagKeyColumnLength) + 1;
subStringEnd = source.IndexOf(endTagKeyColumn, subStringStart);
}
subStringEnd = source.IndexOf(startTagConstraint, subStringStart);
while (subStringEnd > 0)
{
// throw away relationships.
if (subStringEnd - subStringStart > 5)
{
cleanedUp.Append(source.Substring(subStringStart, subStringEnd - subStringStart));
}
subStringStart = source.IndexOf(endTagConstraint, subStringEnd) + endTagConstraintLength;
subStringEnd = source.IndexOf(startTagConstraint, subStringStart);
}
cleanedUp.Append(source.Substring(subStringStart + 1));
target = new DataSet();
using (var reader = new StringReader(cleanedUp.ToString()))
{
target.EnforceConstraints = false;
target.ReadXml(reader, XmlReadMode.Auto);
}
Note, so as I said at the start, I had to fix this problem when we are loading the dataset, and though you are saving the dataset, the workaround will be the same.
The two foreign keys are causing the problem. The other end of the keys are considered to be parents, so you've got two of them. In writing the XML, an element can have only one parent (unless the element appears twice, once under each parent). Possible solutions include removing one of the foreign keys (which I appreciate may break your app in other ways), or, depending on how your dataSet is initialised, try setting EnforceConstraints to false.
Related
I have DataGridView where I am showing data read from database:
DataSet ds = new DataSet();
sqlDa.Fill(ds);
dgView.DataSource = ds.Tables[0]
After adding all of the rows in the UI, I need to to SQL UPDATE of rows that previously read from database, and do INSERT for new rows by clicking Save button (I don't save rows one by one when adding, just all of them when I click the Save button):
foreach (DataGridViewRow dgvRow in dgView.Rows)
{
// do insert for new rows, and update for existing ones from database
}
How can I know what rows are newly added and what are not? Can I add some type of attribute to every row that is read from database so that can I know that they need to be updated?
How can I know what rows are newly added and what are not?
You don't need to; the datatable the DGV is showing is already tracking this. If you make a SqlDataAdapter and plug a SqlCommandBuilder into it see the example code in the docs so that it gains queries in its InsertCommand/UpdateCommand/DeleteCommand properties (or you can put these commands in yourself, but there isn't much point given that a command builder can make them automatically) then you just say:
theDataAdapter.Update(theDataTable);
If you didn't save it anywhere else you can get it from the DataSource of the DGV:
theDataAdapter.Update(dgView.DataSource as DataTable);
Ny the way, the word "Update" here is nothing to do with an update query; Microsoft should have called it SaveChanges. It runs all kinds of modification query (I/U/D) not just UPDATE
If you really want to know, and have a burning desire to reinvent this wheel, you can check a DataRow's RowState property, and it will tell you if it's Added, Modified or Deleted, so you can fire the appropriate query (but genuinely you'd be reimplementing functionality that a SqlDataAdapter already has built in)
All this said, you might not be aware that you can make your life massively easier by:
Add a new DataSet type of file to your project (like you would add a class). Open it
Right-click in the surface of it, choose add TableAdapter
Design your connection string in (once)
Enter your query as a "select that produces rows" like SELECT * FROM SomeTable WHERE ID = Id (it's advisable to use a where clause that selects on the ID; you can add more queries later to do other things, like SELECT * FROM SomeTable WHERE SomeColumn LIKE #someValue but for now selecting on ID gives you a base query to use that is handy for loading related data). You can also use existing or new stored procs if you want
Give it a sensible name pair like FillById, GetDataById - FillBy fills an existing table, Get gets a new one
Finish
You'll now have objects available in your code that are wrappers data adapters and datatables - same functionality but more nicely strongly typed
e.g. you can fill your grid with:
var ta = new SomeTableAdapter();
dgView.DataSource = ta.GetDataByFirstName("John%"); //does select * from table where firstname like 'john%' into a datatable
The datatables are strongly typed, so you don't access them like this:
//no
foreach(DataRow row in someTable.Rows){
if((row["someColumn"] as string) == "hello" && row.IsNull("otherColumn"))
row["otherColumn"] = "goodbye";
}
You have named properties:
//yes
foreach(var row in someTable){
if((row.SomeColumn == "hello" && row.IsOtherColumnNull())
row.OtherColumn = "goodbye";
}
Much nicer. LINQ works on them too, without AsEnumerable or Cast and endless casting the values.
It's not magic; VS writes boatloads of code behind the scenes for you - check in the YourDataSet.Designer.cs file - hundreds of SqlCommands, fully parameterized, for all the table operations (Select/Insert/Update/Delete), all base don typing a SELECT command into a tool pane. It's quite nice to use really, even all these years later.
Oh, but the designer doesn't work very nicely in net core. They're really lagging behind on fixing up the bugs that netcore brings (other priorities)
I'm working in an application dealing with a database having a very dynamic schema. I want to add my database tables schema into a DataSet so that I can get easily my tables column's, type of columns and constraints. I made that possible using the DataAdapter.FillSchema method like this way :
foreach (string table in get_tables())
{
DbDataAdapter myDataAdapter= new SqlDataAdapter("Select * From "+table, myConnexionString);
myDataAdapter.FillSchema(myDataSet, SchemaType.Source, table);
}
where get_tables is a method returning a List<string> of my DataBase tables names. This is working perfectly in my case, but i'm not sure if it's the best way to do it? Is there any alternatives ?
ADO.Net Connection object has a method called GetSchema, which you can use to get the database schema for different objects
string[] restrictions = new string[1];
restrictions[0] = "myTableName";
DataTable table = sqlconnection.GetSchema("Tables",restrictions);
You can see the details in MSDN here:
http://msdn.microsoft.com/en-us/library/ms254934%28v=vs.80%29.aspx
We have created a custom dataset and populating it with some data.
Before adding data, we are adding columns in the data set as follows
DataSet archiveDataset = new DataSet("Archive");
DataTable dsTable = archiveDataset.Tables.Add("Data");
dsTable.Columns.Add("Id", typeof(int));
dsTable.Columns.Add("Name", typeof(string));
dsTable.Columns.Add("LastOperationBy", typeof(int));
dsTable.Columns.Add("Time", typeof(DateTime))
Once the Dataset is create, we are filling values as follows
DataRow dataRow = dsTable.NewRow();
dataRow["Id"] = source.Id;
dataRow["Name"] = source.Name;
dataRow["LastOperationBy"] = source.LastOperationBy;
dataRow["Time"] = source.LaunchTime;
Is there any better and managed way of doing this. can I make the code more easy to write using enum or anything else to reduce the efforts?
You could try using a Typed Dataset.
This should get rid of the ["<column_name>"] ugliness.
If the dataset has a structure similar to tables in a database, then Visual Studio makes it really easy to create one: just click Add -> New Item somewhere in the solution and choose DataSet. VS will show a designer where you can drag tables from your server explorer.
Update (after response to Simon's comment):
A typed dataset is in fact an XSD (XML Schema Definition).
What I did in a similar case was:
created an empty DataSet (using Add -> New Item -> DataSet)
opened the newly created file with a text editor (by dafault, in VS it shows the XSD designer)
paste the XSD that I had created manually
You could also choose to use the designer to create the schema.
Considering your comment "I am using Dataset to export data to a XML file" I recommend using a different technology such as
Linq to XML http://msdn.microsoft.com/en-us/library/bb387061.aspx or
Xml Serialzation http://msdn.microsoft.com/en-us/library/system.xml.serialization.xmlserializer.aspx
Or better yet of is doesnt have to be XML (and you only want hierarchical readable text consider JSON instead http://james.newtonking.com/pages/json-net.aspx
You can bind dataset in two way first one is using database second one is add manually.
After create column for dataset you can add using Loops you can add it if you have 10000 of entries.
You can use Reflection. Another option is to use EntityFramework or NHibernate to map the columnnames and datastructure columns and then avoid these code to fill each field manually. But they will add more complexity. Also Performance wise the your code is better.
Background
Here is my issue. Earlier in the course of my program a System.Data.DataSet was serialized out to a file. Then sometime later the data set schema was changed in the program, specifically a column was added to one of the tables.
This data set has been created using VS and C#, so it has all the properties able to access the rows and columns by name (through the Microsoft generated code). It has all the files (.xsd, .cs, etc.) that VS needs to know what the data set looks like and the names therein.
The file is loaded and saved through XML Serialization. This causes an issue now because when I deserialize the old file it loads in the data related to the old schema. This works for the most part, but the object that is created (the data set) has everything but the column that was added later. So, when trying to access the new column it fails because the deserialization did not know about it and the entire column winds up being null.
This now causes more issues because it throws an exception when trying to access that column (because it's null) through the properties of the data set.
Question
My question is, can I somehow add in the column after deserialization? I apparently need to add it so that it complies with the Microsoft generated code because doing this:
myDataSet.myTable.Columns.Add("MyMissingColumn");
...does not add the column it needs. It may add a column, but the row property myDataRow.MyMissingColumn returns null and errors out.
Do I need to somehow copy the new schema into this object? Again, the only reason this is failing is because the old file was serialized using the old schema.
Any suggestions are appreciated.
Why don't you load the schema from the new schema file, and then load the old data. Provided your column allows nulls it should be fine.
DataSet data = new DataSet();
data.ReadXmlSchema(schemaFile);
data.ReadXml(dataFile, XmlReadMode.IgnoreSchema);
Otherwise just add it on the fly:
if (!data.Tables[0].Columns.Contains("SomeId"))
{
var column = new DataColumn("SomeId", typeof(int));
// give it a default value if you don't want null
column.DefaultValue = 1;
// should it support null values?
column.AllowDBNull = false;
data.Tables[0].Columns.Add(column);
}
you are adding a new column without specify its data type, strange, I would specify typeof(string) using another overload of the Add.
beside this, it's understandable that you cannot do: myDataRow.MyMissingColumn because there was no type/column mapping in the initial version of the XSD, but can you anyway access to this column by name or index?
try something like this
myDataRow["MyMissingColumn"] = "Test";
var s = myDataRow["MyMissingColumn"].ToString();
I've tried to find an answer to do this online but apparently it can't be done (I mean at the app level, not database). I have a need to clear out my dataset completely and reset the primary key at the same time. Any ideas?
Alternatively, one hack i can use is to reinitialize the dataset but that doesn't seem possible as well since the dataset is shared between different classes in the app (I'm creating the shared dataset in Program.cs).
Thanks
Farooq
Update:
ok i tried this:
MyDataSet sharedDS = new MyDataSet();
.
.
.
CleanDS()
{
MyDataSet referenceDS = new MyDataSet();
sharedDS.Table1.Reset();
sharedDS.Merge(referenceDS);
}
My original problem is solved but now I get an System.ArgumentException for Column1 does not belong to Table1 where I can see the columns in the DataSet Viewer as well as see the populated rows. Also note that I can manually re-create the entire DataSet and I still get the same error. Any ideas?
i tried it with the autoincrementseed and autoincrementstep and it finally works. here's for the reference of others:
sharedDS.Clear();
sharedDS.Table1.Columns[0].AutoIncrementStep = -1;
sharedDS.Table1.Columns[0].AutoIncrementSeed = -1;
sharedDS.Table1.Columns[0].AutoIncrementStep = 1;
sharedDS.Table1.Columns[0].AutoIncrementSeed = 1;
please see reasoning in this thread:
http://www.eggheadcafe.com/community/aspnet/10/25407/autoincrementseed.aspx
and:
http://msdn.microsoft.com/en-us/library/system.data.datacolumn.autoincrementseed(VS.85).aspx
thanks all for your help!
Does the DataSet.Clear() method do what you want?
Edit
Because you say you want to reset the primary key, you must be talking about on the DataTables the DataSet holds. Have you tried calling DataSet.Tables["MyTable"].Reset(), which should reset the table to it's original state, rather than the whole DataSet?
Edit 2
If this is an autoincrementing column, have you tried resetting the DataColumn's AutoIncrementSeed property to 0?