To write just the schema, use the WriteXmlSchema method. An object that derives from Stream.
The XmlReadMode used to read the data. The following example creates a DataTable containing two columns and ten rows. The example writes the DataTable schema and data to a memory stream, by invoking the WriteXml method. The example creates a second DataTable and calls the ReadXml method to fill it with schema and data. The current DataTable and its descendents are loaded with the data from the supplied Stream.
The behavior of this method is identical to that of the DataSet. ReadXml method, except that in this case, data is loaded only for the current table and its descendants. If an in-line schema is specified, the in-line schema is used to extend the existing relational structure prior to loading the data. If there are any conflicts for example, the same column in the same table defined with different data types an exception is raised.
If no in-line schema is specified, the relational structure is extended through inference, as necessary, according to the structure of the XML document. If the schema cannot be extended through inference in order to expose all data, an exception is raised.
When legal characters in XML element name are escaped, the element is ignored while processing. The TextReader that will be used to read the data. The current DataTable and its descendents are loaded with the data from the supplied TextReader.
The example writes the DataTable schema and data to disk. The current DataTable and its descendents are loaded with the data from the file named in the supplied String. The XmlReader that will be used to read the data.
The example writes the DataTable schema and data to an XmlReader. The example creates a second DataTable and calls the ReadXml method to fill it with schema and data from the XmlReader instance. The current DataTable and its descendents are loaded with the data from the file named in the supplied XmlReader. The behavior of this method is identical to that of the ReadXml method, except that in this case, data is loaded only for the current table and its descendants.
Skip to main content. Exit focus mode. Data Table. Data Assembly: System. ReadXml Stream. ReadXml TextReader. ReadXml String. ReadXml XmlReader.
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Introduction to DataSets and working with XML files
By continuing to browse this site, you agree to this use. Learn more. Ask a question. Quick access. Search related threads. Remove From My Forums. Answered by:. Visual Studio Languages. NET Framework. Visual C.
Sign in to vote. Hi all I am trying to take an XML response from a web server and putting it into a Dataset I am using a streamreader to pass the xml stream to the readxml method of the dataset, however I am finding that I am not getting all the data.Channel u tv guide
Close. Tuesday, December 9, PM. You don't close the writer either. The using block is going to do it. That may still be your problem. You may need to serialize your stream before you put it in the DataSet and deserialize it on the way back.
Thursday, December 11, PM.
Introduction to DataSets and working with XML files
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I read the instructions here:. Sadly, your snippet of code seem to work on my machine. ReadXml statement executes? The big thing that changed, as you'll notice, is all of the extraneous junk that Visual Studio adds in. NET needs some of this to load the data properly, most notably the primary key annotation. So the moral of the story: if you're going to load a DataSet from XML, create a schema through Visual Studio or be prepared to run it through XSLT to add all this stuff, or the results will be unpredictable, at best.
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Learn more. Ask Question. Asked 6 years, 6 months ago. Active 6 years, 2 months ago. Viewed 2k times. What am I doing wrong? Brad Brad 1, 2 2 gold badges 15 15 silver badges 31 31 bronze badges. I ran your code and it seems to work. What do you mean by the dataset is empty, that there isn't a table in the dataset?
Interesting, this does not work for me either. Auto in your example. Active Oldest Votes. See my output from my Visual Studio immediate window below: ds. I'm absolutely sure. ReadSchema ; if init. Interesting fact ReadSchema parameter, the DataSet is populated, but the only table in it is named "Table1". I finally figured this out. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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DataSet In C#
The Overflow How many jobs can be done at home? Featured on Meta. Community and Moderator guidelines for escalating issues via new response…. Feedback on Q2 Community Roadmap.I'm having trouble reading an xml file into a strongly typed dataset containing a number of tables.Add border to instagram profile picture
It only works if I use InferSchema:. Without InferSchema, I get no data and no error messages. I check this by using a breakpoint and examining db after ReadXml. Should InferSchema ever be used with a typed dataset?? I believe the xml file has the same schema as the dataset, but if there were some differences, what would happen?
Should tables which do match be filled? If there are some extra columns or missing columns in some tables of the xml, or whole missing tables, what would happen? I'm using Visual Studio and I've created the typed dataset using the dataset designer. If they don't match, no data is read without using InferSchema.
If InferSchema is used, the namespaces don't need to match and the DataSet will be populated properly, but or 'and', depending on your point of view any extra columns and tables in the xml file will be added as well. Note that those will not be accessible using notation like mydatasetTable1Row, etc. Without InferSchema, any extra columns and tables in the xml file will be ignored, and values, columns, and tables missing from the xml will just be empty in the dataset.
An additional note - multiple xml files, each containing only 1 or more tables can be read into the same dataset. As long as you don't read the same row more than once, it'll work. Rows are appended then checked for constraints like unique entries, so if you try to read a row containing a column that should be unique twice, you'll get an error.
Check the dataset schema after reading from the file and see the differences. As Radu mentioned, you actually should be using the XmlReadMode. Why is this a good thing? Well, for one thing, it generally will not negatively affect your applicationWorking with them really makes your life easier when you want to share data from a data source and you are thinking of XML.
To compile the solution you need to have Microsoft Visual Studio.
NET installed. To run any of the client executable you need to have the. NET framework installed. The sample provided is a simple application written in C.
It displays a form with a DataGrid. By default, the application connects to a SQL Server, binds the Northwind database and fetches some parent records from table Customers and some child records from table Orders. By default, the application assumes that you have an instance of SQL Server installed on your machine. If this is not the case, then you must manually modify the connection string and then rebuild the sample.
A DataSet object is a very generic object that can store cached data from a database in a very efficient way. It is member of the System::Data namespace. One obvious question is: When to use a dataset? Well, the answer is: it depends. You should consider that a dataset is a collection of in-memory cached data. So it's good to use datasets when:. You can refer the tables later either using the pointers returned by the Add method or like this:.
If you want to specify the data type of a particular column you should use the DataColumn::DataType property. That's it! Well, that's all you have to do if you want to build up your data set manually. This is not how it is done if you want to connect to a real data source. To connect to a database server such as SQL Server and fill a dataset from there you need three additonal objects: a Connectiona DataCommand and a DataAdapter object.
The Connection object is used to connect to the database object. You must provide a connection string to it. Also, if your application is using transactions, you must attach a transaction object to the connection.
The DataCommand object is used to sending commands to the database server. I believe it is obvious what these string objects represent, nothing else but the four basic SQL operations. The DataAdapter object is the object that does all the magic work.A framework for composing real
It fills the DataSet with data from the database and updates data from the DataSet to the database. You may now wonder what are the classes that correspond to the objects described above.
Well, Microsoft have prepared two sets of classes - you can't say life is getting much easier in. NET can you?The contents of an ADO. In addition, with the. NET Framework you have great flexibility over what information is loaded from XML, and how the schema or relational structure of the DataSet is created.
It will also create the relational schema of the DataSet depending on the XmlReadMode specified and whether or not a relational schema already exists.
If you pass an XmlReader to ReadXml that is positioned part of the way into an XML document, ReadXml will read to the next element node and will treat that as the root element, reading until the end of the element node only. This does not apply if you specify XmlReadMode. The first example shows a file name being passed to the ReadXml method. If you call ReadXml to load a very large file, you may encounter slow performance.
To read unqualified elements in this case, set elementFormDefault equal to "qualified" in your XSD schema. For example:. Skip to main content. Exit focus mode. The following table describes the options for the XmlReadMode argument. Option Description Auto This is the default. If you know the format of the XML being read, for best performance it is recommended that you set an explicit XmlReadModerather than accept the Auto default. ReadSchema Reads any inline schema and loads the data and schema.
If the DataSet already contains a schema, new tables are added from the inline schema to the existing schema in the DataSet. If any tables in the inline schema already exist in the DataSetan exception is thrown. You will not be able to modify the schema of an existing table using XmlReadMode. If the DataSet does not contain a schema, and there is no inline schema, no data is read. IgnoreSchema Ignores any inline schema and loads the data into the existing DataSet schema.
Any data that does not match the existing schema is discarded. If no schema exists in the DataSetno data is loaded. InferSchema Ignores any inline schema and infers the schema per the structure of the XML data, then loads the data.In this article I will explain you about ADO. NET in C ". First, you can use ADO. Additionally, you can access a relational database using ADO. NET, you can access the data using the DataSet class.
The following sections discuss methods that read XML data. The ReadXml method has eight overloaded forms. It can read a text, string, stream, TextReader, XmlReader, and their combination formats. In the following example, create a new DataSet object. In the following example, create a new DataSet object and call the DataSet. ReadXml method to load the books. ReadXml "books. Make sure you provide the correct path of books.
Note : Make sure you add a reference to System. Data and the System.Qnap 6 bay
Common namespace before using DataSet and other common data components. It has four overloaded forms. You can use a Text Reader, string, stream, and XmlReader. This is overloaded method. By using this method, you can write data to a file, stream, TextWriter, or XmlWriter.
Listing If you see the output stdData. WriteXmlSchema has four overloaded methods. You can write the data to a stream, text, TextWriter, or Xmlwriter. Listing uses XmlWriter for the output. Figure shows the XmlDataDocument hierarchy. Figure As figure shows, you can take data from two different sources.
First, you can load data from an XML document with the help of XmlReader, and second, you can load data from relational data sources with the help of database provides and DataSet. The neat thing is the data synchronization between these two objects. That means if you update data in a DataSet object, you see results in the XmlDataDocument object and vice versa. For example, if you add a record to a DataSet object, the action will add one node to the XmlDataDocument object representing the newly added record.
Once the data is loaded, you're allowed to use any operations that you were able to use on XmlDocument objects.
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