Lesson 1: Using the ADO.NET Disconnected Classes CHAPTER 7 403 } //write to xml file companyList.WriteXml(MapPath("CompanyListNested.xml")); //display file Response.Redirect("CompanyListNested.xml"); } XML <?xml version="1.0" standalone="yes"?> <CompanyList> <company Id="63cd2a1e-c578-4f21-a826-c5dfb50258b0" CompanyName="Northwind Traders"> <employee Id="a2e7bbba-20ba-4b73-86b3-2d0cca4f1bbb" coId="63cd2a1e-c578-4f21-a826-c5dfb50258b0" LastName="JoeLast" FirstName="JoeFirst" Salary="40" /> <employee Id="5cf475e8-1d97-4784-b72f-84bfbf4a8e14" coId="63cd2a1e-c578-4f21-a826-c5dfb50258b0" LastName="MaryLast" FirstName="MaryFirst" Salary="70" /> <employee Id="55ff1a2b-8956-4ded-99a4-68610134b774" coId="63cd2a1e-c578-4f21-a826-c5dfb50258b0" LastName="SamLast" FirstName="SamFirst" Salary="12" /> </company> <company Id="0adcf278-ccd3-4c3d-a78a-27aa35dc2756" CompanyName="Contoso"> <employee Id="bc431c32-5397-47b6-9a16-0667be455f02" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2756" LastName="SueLast" FirstName="SueFirst" Salary="20" /> <employee Id="5822bf9f-49c1-42dd-95e0-5bb728c5ac60" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2756" LastName="TomLast" FirstName="TomFirst" Salary="68" /> <employee Id="1b2334a4-e339-4255-b826-c0453fda7e61" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2756" LastName="MikeLast" FirstName="MikeFirst" Salary="18.99" /> </company> </CompanyList> In the example, the XML file is written, but the XML file contains no information that describes the data types of the data. When not specified, the default data type for all data is string. If the XML file is read into a new DataSet, all data, including DateTime data and nu- meric data, is loaded as string data. Use the XmlWriteMode.WriteSchema enumeration value when saving because it stores the data type information with the XML file. The resulting XML file is substantially larger. Instead of embedding the schema in the XML file, you can create a separate XSD file to load before loading the data. You can use the 4 0 4 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET DataSet object’s WriteXmlSchema method to extract the XML schema definition to a separate file, as shown here: 'VB 'write to xsd file companyList.WriteXmlSchema( _ MapPath("CompanyListSchema.xsd")) //C# //write to xsd file companyList.WriteXmlSchema( MapPath("CompanyListSchema.xsd")); SERIALIZING A CHANGED DATASET OBJECT AS A DIFFGRAM A DiffGram is an XML document that contains all of the data from your DataSet object, including the original DataRow object information. To save as a DiffGram, use the XmlWrite- Mode.DiffGram enumeration value when serializing a DataSet object. The following code shows the creation of company rows with changes that make it so that one is inserted, one is updated, one is deleted, and one is unchanged. Then the DataSet is written as a DiffGram. 'VB Protected Sub Button11_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles Button11.Click 'get the dataset and populate Dim companyList As DataSet = GetDataSet() Dim company as DataTable = companyList.Tables("company") company.Rows.Add(Guid.NewGuid(), "UnchangedCompany") company.Rows.Add(Guid.NewGuid(), "ModifiedCompany") company.Rows.Add(Guid.NewGuid(), "DeletedCompany") companyList.AcceptChanges() company.Rows(1)("CompanyName") = "ModifiedCompany1" company.Rows(2).Delete() company.Rows.Add(Guid.NewGuid(), "AddedCompany") 'format xml companyList.Relations("Company_Employee").Nested = True For Each dt As DataTable In companyList.Tables For Each dc As DataColumn In dt.Columns dc.ColumnMapping = MappingType.Attribute Next Next 'write to xml diffgram file companyList.WriteXml( _ Lesson 1: Using the ADO.NET Disconnected Classes CHAPTER 7 405 MapPath("companyListDiffGram.xml"), XmlWriteMode.DiffGram) 'display file Response.Redirect("companyListDiffGram.xml") End Sub //C# protected void Button11_Click(object sender, EventArgs e) { //get the dataset and populate DataSet companyList = GetDataSet(); DataTable company = companyList.Tables["company"]; company.Rows.Add(Guid.NewGuid(), "UnchangedCompany"); company.Rows.Add(Guid.NewGuid(), "ModifiedCompany"); company.Rows.Add(Guid.NewGuid(), "DeletedCompany"); companyList.AcceptChanges(); company.Rows[1]["CompanyName"] = "ModifiedCompany1"; company.Rows[2].Delete(); company.Rows.Add(Guid.NewGuid(), "AddedCompany"); //format xml companyList.Relations["Company_Employee"].Nested = true; foreach (DataTable dt in companyList.Tables) { foreach (DataColumn dc in dt.Columns) { dc.ColumnMapping = MappingType.Attribute; } } //write to xml diffgram file companyList.WriteXml( MapPath("CompanyListDiffGram.xml"), XmlWriteMode.DiffGram); //display file Response.Redirect("CompanyListDiffGram.xml"); } The DiffGram is mostly used in an environment where a user occasionally connects to a database to synchronize a disconnected DataSet object with the current information that is contained in the database. When the user is not connected to the database, the DataSet ob- ject is stored locally as a DiffGram to ensure that you still have the original data, because the original data is needed when it’s time to send your changes back to the database. The DiffGram contains all of the DataRowVersion information, as shown in the following XML document. Company1 has not been modified. Notice that Company2 has been modified, and its status is indicated as such. Also notice that the bottom of the XML document contains 406 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET the original information for DataRow objects that have been modified or deleted. This XML document also shows Company3 as deleted because Company3 has “before” information but not current information. Company4 is an inserted DataRow object as indicated, so this DataRow object has no “before” information. <?xml version="1.0" standalone="yes"?> <diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1"> <CompanyList> <company diffgr:id="company1" msdata:rowOrder="0" Id="09b8482c-e801-4c63-82f6-0f5527b3768b" CompanyName="UnchangedCompany" /> <company diffgr:id="company2" msdata:rowOrder="1" diffgr:hasChanges="modified" Id="8f9eceb3-b6de-4da7-84dd-d99a278a23ee" CompanyName="ModifiedCompany1" /> <company diffgr:id="company4" msdata:rowOrder="3" diffgr:hasChanges="inserted" Id="65d28892-b8af-4392-8b64-718a612f6aa7" CompanyName="AddedCompany" /> </CompanyList> <diffgr:before> <company diffgr:id="company2" msdata:rowOrder="1" Id="8f9eceb3-b6de-4da7-84dd-d99a278a23ee" CompanyName="ModifiedCompany" /> <company diffgr:id="company3" msdata:rowOrder="2" Id="89b576d2-60ae-4c36-ba96-c4a7a8966a6f" CompanyName="DeletedCompany" /> </diffgr:before> </diffgr:diffgram> DESERIALIZING A DATASET FROM XML You can deserialize an XML file or stream into a DataSet object by loading the schema and reading the stream. You can use the following code to read the schema file and load the XML file: 'VB Protected Sub Button12_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles Button12.Click 'get the dataset and populate schema Dim companyList as new DataSet() companyList.ReadXmlSchema(MapPath("CompanyListSchema.xsd")) 'populate from file companyList.ReadXml(MapPath("CompanyListNested.xml")) Lesson 1: Using the ADO.NET Disconnected Classes CHAPTER 7 407 'display GridViewCompany.DataSource = companyList GridViewCompany.DataMember = "Company" GridViewEmployee.DataSource = companyList GridViewEmployee.DataMember = "Employee" GridViewCompany.DataBind() GridViewEmployee.DataBind() End Sub //C# protected void Button12_Click(object sender, EventArgs e) { //get the dataset and populate schema DataSet companyList = new DataSet(); companyList.ReadXmlSchema(MapPath("CompanyListSchema.xsd")); //populate from file companyList.ReadXml(MapPath("CompanyListNested.xml")); //display GridViewCompany.DataSource = companyList; GridViewCompany.DataMember = "Company"; GridViewEmployee.DataSource = companyList; GridViewEmployee.DataMember = "Employee"; GridViewCompany.DataBind(); GridViewEmployee.DataBind(); } When reading an XML file, you can optionally pass an XmlReadMode enumeration value. If this value is not passed, the default is XmlReadMode.IgnoreSchema. This means that if the XML data file contains an XSD, it is ignored. Listed here are the other options of the XmlRead- Mode enumeration: n Auto The XML source is examined by the ReadXml method and the appropriate mode is selected. n DiffGram If the XmlFile contains a DiffGram, the changes are applied to the Data- Set using the same semantics that the Merge method uses. (Merge is covered in more detail in the section “Using Merge to Combine DataSet Data.”) n Fragment This option causes the XML to be read as a fragment. Fragments can con- tain multiple root elements. FOR XML in SQL Server is an example of something that produces fragments. 408 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET n IgnoreSchema This causes any schema that is defined within the XML data file to be ignored. n InferSchema Using this option, the XML file is read, and the DataTable objects and DataColumn objects are created based on the data. If the DataSet currently has Data- Table objects and DataColumn objects, they are used and extended to accommodate new tables and columns that exist in the XML document, but don’t exist in the DataSet object. All data types of all DataColumn objects are a string. n InferTypedSchema Using this option, the XML file is read, and the schema is created based on the data. An attempt is made to identify the data type of each column, but if the data type cannot be identified, it is a string. n ReadSchema Using this option, the XML file is read, and then an embedded schema is searched for. If the DataSet already has DataTable objects with the same name, an exception is thrown. All other existing tables remain. Inferring a schema simply means that the DataSet attempts to create a schema for the data based on looking for patterns of XML elements and attributes. SERIALIZING THE DATASET OBJECT AS BINARY DATA The size of an XML file that is produced when serializing a DataSet object can cause prob- lems with resources, such as memory and drive space or bandwidth when you move this data across the network. If XML is not required and you want the best performance, the DataSet can be serialized as a binary file. The following code writes the contents of the vendorData DataSet that we previously defined and populated to a binary file: 'VB 'Add the following Imports statements to the top of the file Imports System.Runtime.Serialization.Formatters.Binary Imports System.IO Protected Sub Button13_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles Button13.Click 'get the dataset and populate Dim companyList As DataSet = GetDataSet() 'set output to binary else this will be xml companyList.RemotingFormat = SerializationFormat.Binary 'write to binary file Using fs As New FileStream( _ MapPath("CompanyList.bin"), FileMode.Create) Dim fmt As New BinaryFormatter() fmt.Serialize(fs, companyList) Lesson 1: Using the ADO.NET Disconnected Classes CHAPTER 7 409 End Using 'feedback Label1.Text = "File Saved." End Sub //C# //Add the following using statements to the top of the file using System.Runtime.Serialization.Formatters.Binary; using System.IO; protected void Button13_Click(object sender, EventArgs e) { //get the dataset and populate DataSet companyList = GetDataSet(); //set output to binary else this will be xml companyList.RemotingFormat = SerializationFormat.Binary; //write to binary file using (FileStream fs = new FileStream(MapPath("CompanyList.bin"), FileMode.Create)) { BinaryFormatter fmt = new BinaryFormatter(); fmt.Serialize(fs, companyList); } //feedback Label1.Text = "File Saved."; } The DataSet object’s RemotingFormat property must be set to ensure binary serializa- tion. This property is also available on the DataTable object for scenarios where only a single DataTable is to be binary serialized. Be careful when making the choice to serialize as XML or binary, because binary files contain more initial overhead (about 20 kilobytes) than XML files. For large DataSet objects, binary serialization always produces a smaller file, but for small DataSet objects, binary serialization might not produce smaller output. DESERIALIZING A DATASET FROM BINARY DATA You can easily deserialize the binary data file that we created in the previous example into a DataSet from a file or stream. The BinaryFormatter stores the schema automatically, so there is no need to load a schema first. The BinaryFormatter automatically identifies the file as having been saved as BinaryXml. You can use the following code to load the binary file and display the companyList: 4 1 0 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET 'VB Protected Sub Button14_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles Button14.Click 'get the dataset from the file Dim companyList As DataSet Using fs As New FileStream( _ MapPath("CompanyList.bin"), FileMode.Open) Dim fmt As New BinaryFormatter() companyList = CType(fmt.Deserialize(fs), DataSet) End Using 'display GridViewCompany.DataSource = companyList GridViewCompany.DataMember = "Company" GridViewEmployee.DataSource = companyList GridViewEmployee.DataMember = "Employee" GridViewCompany.DataBind() GridViewEmployee.DataBind() End Sub //C# protected void Button14_Click(object sender, EventArgs e) { //get the dataset from the file DataSet companyList; using (FileStream fs = new FileStream( MapPath("CompanyList.bin"), FileMode.Open)) { BinaryFormatter fmt = new BinaryFormatter(); companyList = (DataSet)fmt.Deserialize(fs); } //display GridViewCompany.DataSource = companyList; GridViewCompany.DataMember = "Company"; GridViewEmployee.DataSource = companyList; GridViewEmployee.DataMember = "Employee"; GridViewCompany.DataBind(); GridViewEmployee.DataBind(); } Lesson 1: Using the ADO.NET Disconnected Classes CHAPTER 7 411 USING MERGE TO COMBINE DATASET DATA On many occasions, data available in one DataSet must be combined with another DataSet. For example, an expense application might need to combine serialized DataSet objects (ex- pense reports) received by e-mail from a number of people. It’s also common within an ap- plication (based on the user clicking Update) to merge a modified version back to the original DataSet. The Merge method on the DataSet is used to combine data from multiple DataSet objects. The Merge method has several overloads that allow data to be merged from DataSet, Data- Table, or DataRow objects. The following code example demonstrates how to use the Merge method to combine changes from one DataSet into another DataSet: 'VB Protected Sub Button15_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles Button15.Click 'get the dataset Dim original As DataSet = GetDataSet() 'add AdventureWorks original.Tables("Company").Rows.Add( _ Guid.NewGuid(), "AdventureWorks") 'copy the dataset Dim copy as DataSet = original.Copy() 'modify the copy Dim aw as DataRow = copy.Tables("Company").Rows(0) aw("CompanyName") = "AdventureWorks Changed" Dim empId as Guid empId = Guid.NewGuid() copy.Tables("Employee").Rows.Add(empId, aw("Id"), _ "MarkLast", "MarkFirst", 90.00) empId = Guid.NewGuid() copy.Tables("Employee").Rows.Add(empId, aw("Id"), _ "SueLast", "SueFirst", 41.00) 'merge changes back to the original original.Merge(copy, False, MissingSchemaAction.AddWithKey) 'display GridViewCompany.DataSource = original GridViewCompany.DataMember = "company" GridViewEmployee.DataSource = original 4 1 2 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET GridViewEmployee.DataMember = "employee" GridViewCompany.DataBind() GridViewEmployee.DataBind() End Sub //C# protected void Button15_Click(object sender, EventArgs e) { //get the dataset DataSet original = GetDataSet(); //add AdventureWorks original.Tables["Company"].Rows.Add( Guid.NewGuid(), "AdventureWorks"); //copy the dataset DataSet copy = original.Copy(); //modify the copy DataRow aw = copy.Tables["Company"].Rows[0]; aw["CompanyName"] = "AdventureWorks Changed"; Guid empId; empId = Guid.NewGuid(); copy.Tables["Employee"].Rows.Add(empId, aw["Id"], "MarkLast", "MarkFirst", 90.00m); empId = Guid.NewGuid(); copy.Tables["employee"].Rows.Add(empId, aw["Id"], "SueLast", "SueFirst", 41.00m); //merge changes back to the original original.Merge(copy, false, MissingSchemaAction.AddWithKey); //display GridViewCompany.DataSource = original; GridViewCompany.DataMember = "Company"; GridViewEmployee.DataSource = original; GridViewEmployee.DataMember = "Employee"; GridViewCompany.DataBind(); GridViewEmployee.DataBind(); } The Merge method is always called on the original DataSet (that you will merge into); it takes three parameters. The first parameter is the object to be merged. The second parameter is a Boolean that specifies whether updates from the DataSet to be merged should overwrite changes made in the original object. The last parameter is a MissingSchemaAction enumera- tion member. If AddWithKey is specified, as in this example, a new DataTable has been added [...]... DataSet D Use the Group By clause in your code to group by active vendors CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET Lesson 2: using the adO.net connected classes The ADO.NET libraries contain provider classes, which are classes that you can use to transfer data between a data store and the client application There are many different kinds of data stores, meaning that there is a need for specialized... xmlns="http://www.w3.org/2001/04/xmlenc#"> Rsa Key 4 34 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET PPWA1TkWxs2i698Dj07iLUberpFYIj6wBhbmqfmNK/plarau4i1k+xq5bZzB4VJW8 OkhwzcIIdZIXff6INJ1wlZz76ZV1DIbRzbH71t6d/L/qJtuOexXxTi2LrepreK/q3svMLpsJycnDPa... referred to as provider classes in the framework There is a provider framework on which these classes are built This ensures that each provider is written in a similar manner and only the implementation code changes These provider classes represent the bridge between the database and the disconnected data classes discussed in the prior lesson The Microsoft NET Framework contains the following data access... general-purpose data access to many data sources You can use this provider to access Microsoft SQL Server 6 .5 (and earlier versions), SyBase, DB2/400, and Microsoft Access n Odbc This contains classes for general-purpose data access to many data sources This provider is typically used when no newer provider is available Lesson 2: Using the ADO.NET Connected Classes CHAPTER 7 421 Server  This contains classes that... object, you must close the connection to free up the resources being held The pubs sample database is used in this example The pubs and 4 22 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET Northwind sample databases are available from the Microsoft download site and are also included in the samples installed from the CD Figure 7-9  The DbConnection class hierarchy 'VB Dim connection as DbConnection... connection Typically, the physical path to a data source CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET WOrkinG with Sample ODBC COnnectiOn StrinGs The following connection string instructs the text driver to treat the files that are located in the C:\Sample\MySampleFolder subdirectory as tables in a database: Driver= {Microsoft Text Driver (*.txt; *.csv)}; DBQ=C:\\Sample\\MySampleFolder; The following... support provider for database mirroring in SQL Server CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET Keyword AttachDbFilename, extended properties, initial file name The full or relative path and name of a file containing the database to be attached to The path supports the keyword string |DataDirectory|, which points to the application s data directory The database must reside on a local drive... Integrated Security=SSPI; database=northwind; 4 28 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET server=localhost; Connect Timeout=30 This next connection string uses the Transmission Control Protocol (TCP) sockets library (DBMSSOCN) and connects to the MyDbName database on the computer located at Internet Protocol (IP) address 192.168.1 .5, using port 1433 Authentication is based on using MyUsername... in seconds to wait while a connection to the data store is attempted The default is 15 seconds n Min Pool Size  The minimum amount of pooled connections to keep in the pool The default is 0 It’s usually good to set this to a low number, such as 5, when your application requires consistent, fast response, even if the application is inactive for long periods of time n Max Pool Size  The maximum allowed... salesDataSet; DataBind(); } } 9 Run the Web page Figure 7-8 shows the results figure 7-8 The typed DataSet populated and bound to the GridView control 418 CHAPTER 7 Using ADO.NET, XML, and LINQ with ASP.NET Lesson Summary n This lesson covers ADO.NET’s disconnected classes When you work with disconnected data, a DataTable object is always required n The DataTable object contains DataColumn objects, which define . Id="0adcf278-ccd3-4c3d-a78a-27aa35dc2 756 " CompanyName="Contoso"> <employee Id="bc 431 c32- 53 9 7-47b6-9a16-0667be 455 f02" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2 756 " LastName="SueLast". Salary="68" /> <employee Id="1b 233 4a4-e 339 -4 255 -b826-c0 453 fda7e61" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2 756 " LastName="MikeLast" FirstName="MikeFirst". Salary="20" /> <employee Id=" ;58 22bf9f-49c1-42dd-95e0-5bb728c5ac60" coId="0adcf278-ccd3-4c3d-a78a-27aa35dc2 756 " LastName="TomLast" FirstName="TomFirst"