DataSet.GetXml Metodo

Riferimento

Definizione

Spazio dei nomi:: System.Data

Assembly:: System.Data.Common.dll

Assembly:: System.Data.dll

Assembly:: netstandard.dll

Source:: DataSet.cs

Source:: DataSet.cs

Source:: DataSet.cs

Importante

Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.

Restituisce la rappresentazione XML dei dati memorizzati nell'oggetto DataSet.

public:
 System::String ^ GetXml();

public string GetXml ();

member this.GetXml : unit -> string

Public Function GetXml () As String

Restituisce

String

Stringa che costituisce una rappresentazione dei dati memorizzati nell'oggetto DataSet.

Esempio

Nell'esempio seguente viene creato un DataSet oggetto e DataTable, vengono aggiunti dati di esempio e quindi vengono visualizzati i dati in formato XML.

private static void DemonstrateGetXml()
{
    // Create a DataSet with one table containing
    // two columns and 10 rows.
    DataSet dataSet = new DataSet("dataSet");
    DataTable table = dataSet.Tables.Add("Items");
    table.Columns.Add("id", typeof(int));
    table.Columns.Add("Item", typeof(string));

    // Add ten rows.
    DataRow row;
    for(int i = 0; i <10;i++)
    {
        row = table.NewRow();
        row["id"]= i;
        row["Item"]= "Item" + i;
        table.Rows.Add(row);
    }

    // Display the DataSet contents as XML.
    Console.WriteLine( dataSet.GetXml() );
}

Private Shared Sub DemonstrateGetXml()
    ' Create a DataSet with one table 
    ' containing two columns and 10 rows.
    Dim dataSet As New DataSet("dataSet")
    Dim table As DataTable = dataSet.Tables.Add("Items")
    table.Columns.Add("id", Type.GetType("System.Int32"))
    table.Columns.Add("Item", Type.GetType("System.String"))

    ' Add ten rows.
    Dim row As DataRow
    Dim i As Integer
    For i = 0 To 9
        row = table.NewRow()
        row("id") = i
        row("Item")= "Item" & i
        table.Rows.Add(row)
    Next

    ' Display the DataSet contents as XML.
    Console.WriteLine( dataSet.GetXml() )
End Sub

In questo esempio viene illustrato come scrivere i dati in un file XML da un DataSet e leggere tali dati nel DataSet di XML. In questo esempio verrà creato un dataset con due tabelle. Utilizzare due modalità per esportare un set di dati nei file XML (WriteXml e GetXml) e utilizzare due modalità (ReadXml e InferXmlSchema) per includere un set di dati dal file XML.

Prima di compilare ed eseguire l'esempio, è necessario creare quattro file XML nella directory dell'esempio. Creare innanzitutto ElementsWithAttributes.xml:

<MySchool>
  <Course CourseID="C1045" Year="2012"  Title="Calculus" Credits="4" DepartmentID="7">New</Course>
  <Course CourseID="C1061" Year="2012"  Title="Physics" Credits="4" DepartmentID="1" />
  <Department DepartmentID="1" Name="Engineering" Budget="350000" StartDate="2007-09-01T00:00:00+08:00" Administrator="2" />
  <Department DepartmentID="7" Name="Mathematics" Budget="250024" StartDate="2007-09-01T00:00:00+08:00" Administrator="3">Cancelled</Department>
</MySchool>

Creare quindi ElementsWithChildElementsxml.xml:

<MySchool>
  <Course>
    <CourseID>C1045</CourseID>
    <Year>2012</Year>
    <Title>Calculus</Title>
    <Credits>4</Credits>
    <DepartmentID>7</DepartmentID>
  </Course>
  <Course>
    <CourseID>C1061</CourseID>
    <Year>2012</Year>
    <Title>Physics</Title>
    <Credits>4</Credits>
    <DepartmentID>1</DepartmentID>
  </Course>
  <Course>
    <CourseID>C2021</CourseID>
    <Year>2012</Year>
    <Title>Composition</Title>
    <Credits>3</Credits>
    <DepartmentID>2</DepartmentID>
  </Course>
  <Course>
    <CourseID>C2042</CourseID>
    <Year>2012</Year>
    <Title>Literature</Title>
    <Credits>4</Credits>
    <DepartmentID>2</DepartmentID>
  </Course>
  <Department>
    <DepartmentID>1</DepartmentID>
    <Name>Engineering</Name>
    <Budget>350000</Budget>
    <StartDate>2007-09-01T00:00:00+08:00</StartDate>
    <Administrator>2</Administrator>
  </Department>
  <Department>
    <DepartmentID>2</DepartmentID>
    <Name>English</Name>
    <Budget>120000</Budget>
    <StartDate>2007-09-01T00:00:00+08:00</StartDate>
    <Administrator>6</Administrator>
  </Department>
  <Department>
    <DepartmentID>4</DepartmentID>
    <Name>Economics</Name>
    <Budget>200000</Budget>
    <StartDate>2007-09-01T00:00:00+08:00</StartDate>
    <Administrator>4</Administrator>
  </Department>
  <Department>
    <DepartmentID>7</DepartmentID>
    <Name>Mathematics</Name>
    <Budget>250024</Budget>
    <StartDate>2007-09-01T00:00:00+08:00</StartDate>
    <Administrator>3</Administrator>
  </Department>
</MySchool>

Creare ora ElementsWithOnlyAttributes.xml:

<MySchool>
  <Course CourseID="C1045" Year="2012"  Title="Calculus" Credits="4" DepartmentID="7" />
  <Course CourseID="C1061" Year="2012"  Title="Physics" Credits="4" DepartmentID="1" />
  <Department DepartmentID="1" Name="Engineering" Budget="350000" StartDate="2007-09-01T00:00:00+08:00" Administrator="2" />
  <Department DepartmentID="7" Name="Mathematics" Budget="250024" StartDate="2007-09-01T00:00:00+08:00" Administrator="3" />
</MySchool>

Creare infine RepeatingElements.xml:

<MySchool>
  <Course>C1045</Course>
  <Course>C1061</Course>
  <Department>Engineering</Department>
  <Department>Mathematics</Department>
</MySchool>

Ora è possibile compilare ed eseguire il codice sorgente.

using System;
using System.Data;
using System.IO;
using System.Text;
using System.Xml;

// Use WriteXml method to export the dataset.
static class DataTableHelper {
   public static void WriteDataSetToXML(DataSet dataset, String xmlFileName) {
      using (FileStream fsWriterStream = new FileStream(xmlFileName, FileMode.Create)) {
         using (XmlTextWriter xmlWriter = new XmlTextWriter(fsWriterStream, Encoding.Unicode)) {
            dataset.WriteXml(xmlWriter, XmlWriteMode.WriteSchema);
            Console.WriteLine("Write {0} to the File {1}.", dataset.DataSetName, xmlFileName);
            Console.WriteLine();
         }
      }
   }

   // Use GetXml method to get the XML data of the dataset and then export to the file.
   public static void GetXMLFromDataSet(DataSet dataset, String xmlFileName) {
      using (StreamWriter writer = new StreamWriter(xmlFileName)) {
         writer.WriteLine(dataset.GetXml());
         Console.WriteLine("Get Xml data from {0} and write to the File {1}.", dataset.DataSetName, xmlFileName);
         Console.WriteLine();
      }
   }

   // Use ReadXml method to import the dataset from the dataset.
   public static void ReadXmlIntoDataSet(DataSet newDataSet, String xmlFileName) {
      using (FileStream fsReaderStream = new FileStream(xmlFileName, FileMode.Open)) {
         using (XmlTextReader xmlReader = new XmlTextReader(fsReaderStream)) {
            newDataSet.ReadXml(xmlReader, XmlReadMode.ReadSchema);
         }
      }
   }

   // Display the columns and value of DataSet.
   public static void ShowDataSet(DataSet dataset) {
      foreach (DataTable table in dataset.Tables) {
         Console.WriteLine("Table {0}:", table.TableName);
         ShowDataTable(table);
      }
   }

   // Display the columns and value of DataTable.
   private static void ShowDataTable(DataTable table) {
      foreach (DataColumn col in table.Columns) {
         Console.Write("{0,-14}", col.ColumnName);
      }
      Console.WriteLine("{0,-14}", "");

      foreach (DataRow row in table.Rows) {
         if (row.RowState == DataRowState.Deleted) {
            foreach (DataColumn col in table.Columns) {
               if (col.DataType.Equals(typeof(DateTime))) {
                  Console.Write("{0,-14:d}", row[col, DataRowVersion.Original]);
               }
               else if (col.DataType.Equals(typeof(Decimal))) {
                  Console.Write("{0,-14:C}", row[col, DataRowVersion.Original]);
               }
               else {
                  Console.Write("{0,-14}", row[col, DataRowVersion.Original]);
               }
            }
         }
         else {
            foreach (DataColumn col in table.Columns) {
               if (col.DataType.Equals(typeof(DateTime))) {
                  Console.Write("{0,-14:d}", row[col]);
               }
               else if (col.DataType.Equals(typeof(Decimal))) {
                  Console.Write("{0,-14:C}", row[col]);
               }
               else {
                  Console.Write("{0,-14}", row[col]);
               }
            }
         }
         Console.WriteLine("{0,-14}", "");
      }
   }

   // Display the columns of DataSet.
   public static void ShowDataSetSchema(DataSet dataSet) {
      Console.WriteLine("{0} contains the following tables:", dataSet.DataSetName);
      foreach (DataTable table in dataSet.Tables) {
         Console.WriteLine("   Table {0} contains the following columns:", table.TableName);
         ShowDataTableSchema(table);
      }
   }

   // Display the columns of DataTable
   private static void ShowDataTableSchema(DataTable table) {
      String columnString = "";
      foreach (DataColumn col in table.Columns) {
         columnString += col.ColumnName + "   ";
      }
      Console.WriteLine(columnString);
   }
}

class Program {
   static void Main(string[] args) {
      // Create the DataSet
      DataSet school = new DataSet("MySchool");
      DataTable course = CreateCourse();
      DataTable department = CreateDepartment();
      school.Tables.Add(course);
      school.Tables.Add(department);

      // Define the constraint between the tables.
      ForeignKeyConstraint courseDepartFK = new ForeignKeyConstraint("CourseDepartFK", department.Columns["DepartmentID"], course.Columns["DepartmentID"]);
      courseDepartFK.DeleteRule = Rule.Cascade;
      courseDepartFK.UpdateRule = Rule.Cascade;
      courseDepartFK.AcceptRejectRule = AcceptRejectRule.None;
      course.Constraints.Add(courseDepartFK);

      InsertDepartments(department);
      InsertCourses(course);

      // Export the dataset to the XML file.
      Console.WriteLine("Data of the whole DataSet {0}", school.DataSetName);
      DataTableHelper.ShowDataSet(school);

      String xmlWithSchemaFileName = "WriterXMLWithSchema.xml";
      String xmlGetDataFileName = "GetXML.xml";

      // Use two ways to export the dataset to the Xml file.
      DataTableHelper.WriteDataSetToXML(school, xmlWithSchemaFileName);
      DataTableHelper.GetXMLFromDataSet(school, xmlGetDataFileName);

      // Import the dataset from the XML file.
      // Use two ways to import the dataset from the Xml file.
      Console.WriteLine("Read Xml document into a new DataSet:");
      DataSet newSchool = new DataSet("NewSchool");
      DataTableHelper.ReadXmlIntoDataSet(newSchool, xmlWithSchemaFileName);
      DataTableHelper.ShowDataSetSchema(newSchool);
      Console.WriteLine();

      Console.WriteLine("Infer a schema for a DataSet from an XML document:");
      InferDataSetSchemaFromXml();

      Console.WriteLine("Press any key to exit.");
      Console.ReadKey();
   }

   static DataTable CreateCourse() {
      DataTable course = new DataTable("Course");
      DataColumn[] cols ={
                              new DataColumn("CourseID",typeof(String)),
                              new DataColumn("Year",typeof(Int32)),
                              new DataColumn("Title",typeof(String)),
                              new DataColumn("Credits",typeof(Int32)),
                              new DataColumn("DepartmentID",typeof(Int32))};
      course.Columns.AddRange(cols);

      course.PrimaryKey = new DataColumn[] { course.Columns["CourseID"], course.Columns["Year"] };

      return course;
   }

   static DataTable CreateDepartment() {
      DataTable department = new DataTable("Department");
      DataColumn[] cols = {
                                new DataColumn("DepartmentID", typeof(Int32)),
                                new DataColumn("Name",typeof(String)),
                                new DataColumn("Budget",typeof(Decimal)),
                                new DataColumn("StartDate",typeof(DateTime)),
                                new DataColumn("Administrator",typeof(Int32))};
      department.Columns.AddRange(cols);

      department.PrimaryKey = new DataColumn[] { department.Columns["DepartmentID"] };

      return department;
   }

   static void InsertDepartments(DataTable department) {
      Object[] rows = {
                            new Object[]{1,"Engineering",350000.00,new DateTime(2007,9,1),2},
                            new Object[]{2,"English",120000.00,new DateTime(2007,9,1),6},
                            new Object[]{4,"Economics",200000.00,new DateTime(2007,9,1),4},
                            new Object[]{7,"Mathematics",250024.00,new DateTime(2007,9,1),3}};

      foreach (Object[] row in rows) {
         department.Rows.Add(row);
      }
   }

   static void InsertCourses(DataTable course) {
      Object[] rows ={
                               new Object[]{"C1045",2012,"Calculus",4,7},
                               new Object[]{"C1061",2012,"Physics",4,1},
                               new Object[]{"C2021",2012,"Composition",3,2},
                               new Object[]{"C2042",2012,"Literature",4,2}};

      foreach (Object[] row in rows) {
         course.Rows.Add(row);
      }
   }

   // Display the results of inferring schema from four types of XML structures
   private static void InferDataSetSchemaFromXml() {
      String[] xmlFileNames = {

                                    @"ElementsWithOnlyAttributes.xml",
                                    @"ElementsWithAttributes.xml",
                                    @"RepeatingElements.xml",
                                    @"ElementsWithChildElements.xml" };

      foreach (String xmlFileName in xmlFileNames) {
         Console.WriteLine("Result of {0}", Path.GetFileNameWithoutExtension(xmlFileName));
         DataSet newSchool = new DataSet();
         newSchool.InferXmlSchema(xmlFileName, null);
         DataTableHelper.ShowDataSetSchema(newSchool);
         Console.WriteLine();
      }
   }
}

Commenti

La chiamata a questo metodo è identica alla chiamata WriteXml con XmlWriteMode impostata su IgnoreSchema.

GetXml restituisce XML come stringa e pertanto richiede un sovraccarico maggiore di quello di WriteXml scrivere XML in un file.

Se si compila un oggetto usando l'inferenza DataSet dello schema e serializzarlo usando i servizi XML o Web, l'ordinamento delle colonne può cambiare.

Si applica a

Vedi anche

Uso di DataSet in ADO.NET

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