DataSet.GetXml Metod

public:
 System::String ^ GetXml();

[System.Diagnostics.CodeAnalysis.RequiresDynamicCode("Members from serialized types may use dynamic code generation.")]
[System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from serialized types may be trimmed if not referenced directly.")]
public string GetXml();

public string GetXml();

[System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from serialized types may be trimmed if not referenced directly.")]
public string GetXml();

[<System.Diagnostics.CodeAnalysis.RequiresDynamicCode("Members from serialized types may use dynamic code generation.")>]
[<System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from serialized types may be trimmed if not referenced directly.")>]
member this.GetXml : unit -> string

member this.GetXml : unit -> string

[<System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode("Members from serialized types may be trimmed if not referenced directly.")>]
member this.GetXml : unit -> string

Public Function GetXml () As String

Returer

En sträng som är en representation av data som lagras i DataSet.

Attribut

RequiresDynamicCodeAttribute RequiresUnreferencedCodeAttribute

Exempel

I följande exempel skapas en DataSet och DataTable, lägger till exempeldata och visar sedan data i XML-format.

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

Det här exemplet visar hur du skriver data till en XML-fil från en DataSet och läser data till DataSet från XML. Det här exemplet skapar en datauppsättning med två tabeller, använder två sätt att exportera en datauppsättning till XML-filerna (WriteXml och GetXml) och använder två sätt (ReadXml och InferXmlSchema) för att importera en datamängd från XML-filerna.

Innan du kompilerar och kör exemplet måste du skapa fyra XML-filer i exempelkatalogen. Skapa först 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>

Skapa sedan 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>

Skapa nu 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>

Och slutligen skapar du RepeatingElements.xml:

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

Nu kan du kompilera och köra följande källkod.

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();
      }
   }
}

Kommentarer

Att anropa den här metoden är identiskt med anrop WriteXml med XmlWriteMode inställt på IgnoreSchema.

GetXml returnerar XML som en sträng och kräver därför mer omkostnader än WriteXml att skriva XML till en fil.

Om du skapar en DataSet med hjälp av schemainferens och serialiserar den med xml- eller webbtjänster kan kolumnordningen ändras.

Se även

• Använda datauppsättningar i ADO.NET