此示例阐释如何将内部数据集 (DataSet) 映射保存到 XML 架构定义语言 (XSD) 架构文件中。此示例通过使用数据集上的关系方法生成映射以创建表和列。然后,该示例将这些映射的 XSD 架构表示形式写到文件中。
[ 运行示例] | [ 查看源代码] |
DataSet 和 XmlDataDocument 类都表示内存中的数据缓存。DataSet 提供面向关系的导航和编辑方法,而 XmlDataDocument 提供 XML 导航和编辑方法。
此示例从 XmlDataDocument 获取 DataSet 属性,使用该属性生成一组表和列,然后填充这些表和列。然后,该示例写出内部生成的架构。
下列示例代码生成两个表,一个用于人,另一个用于宠物。该示例使用 ID 作为每个表的主关键字,并建立人和他们的宠物之间的关系表。为此,该示例首先创建 XmlDataDocument 的一个实例,然后将与 XmlDataDocument 关联的数据集传递给 LoadDataSet 方法。
XmlDataDocument datadoc = new XmlDataDocument(); LoadDataSet(datadoc.DataSet); Dim datadoc As XmlDataDocument = New XmlDataDocument() LoadDataSet(datadoc.DataSet) |
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C# | VB |
LoadDataSet 方法使用关系数据加载数据集。
// Load a DataSet with relational data private void LoadDataSet(DataSet dataset) { try { Console.WriteLine("Loading the DataSet ..."); // Set DataSet name dataset.DataSetName = "PersonPet"; // Create tables for people and pets DataTable people = new DataTable("Person"); DataTable pets = new DataTable("Pet"); // Set up the columns in the Tables DataColumn personname = new DataColumn ("Name", typeof(String)); DataColumn personAge = new DataColumn ("Age", typeof(Int32)); DataColumn petname = new DataColumn ("Name", typeof(String)); DataColumn pettype = new DataColumn ("Type", typeof(String)); // Add columns to person table DataColumn id = people.Columns.Add("ID", typeof(Int32)); id.AutoIncrement = true; people.PrimaryKey = new DataColumn[] {id}; people.Columns.Add (personname); people.Columns.Add (personAge); // Add columns to pet table id = pets.Columns.Add("ID", typeof(Int32)); id.AutoIncrement = true; pets.PrimaryKey = new DataColumn[] {id}; id.AutoIncrement = true; DataColumn ownerid = pets.Columns.Add("OwnerID", typeof(Int32)); DataColumn[] foreignkey = new DataColumn[] {ownerid}; pets.Columns.Add (petname); pets.Columns.Add (pettype); // Add tables to the DataSet dataset.Tables.Add (people); dataset.Tables.Add (pets); // Add people DataRow mark = people.NewRow(); mark[personname] = "Mark"; mark[personAge] = 18; people.Rows.Add(mark); DataRow william = people.NewRow(); william[personname] = "William"; william[personAge] = 12; people.Rows.Add(william); DataRow james = people.NewRow(); james[personname] = "James"; james[personAge] = 7; people.Rows.Add(james); DataRow levi = people.NewRow(); levi[personname] = "Levi"; levi[personAge] = 4; people.Rows.Add(levi); // Add relationships Console.WriteLine("Creating relationships between people and pets ..."); DataRelation personpetrel = new DataRelation ("PersonPet",people.PrimaryKey, foreignkey); dataset.Relations.Add (personpetrel); // Add pets DataRow row = pets.NewRow(); row["OwnerID"] = mark["ID"]; row[petname] = "Frank"; row[pettype] = "cat"; pets.Rows.Add(row); row = pets.NewRow(); row["OwnerID"] = william["ID"]; row[petname] = "Rex"; row[pettype] = "dog"; pets.Rows.Add(row); row = pets.NewRow(); row["OwnerID"] = james["ID"]; row[petname] = "Cottontail"; row[pettype] = "rabbit"; pets.Rows.Add(row); row = pets.NewRow(); row["OwnerID"] = levi["ID"]; row[petname] = "Sid"; row[pettype] = "snake"; pets.Rows.Add(row); row = pets.NewRow(); row["OwnerID"] = levi["ID"]; row[petname] = "Tickles"; row[pettype] = "spider"; pets.Rows.Add(row); row = pets.NewRow(); row["OwnerID"] = william["ID"]; row[petname] = "Tweetie"; row[pettype] = "canary"; pets.Rows.Add(row); // commit changes dataset.AcceptChanges(); } catch (Exception e) { Console.WriteLine("Exception: {0}", e.ToString()); } } ' Load a DataSet with relational data private sub LoadDataSet(dataset as DataSet) try Console.WriteLine("Loading the DataSet ...") ' Set DataSet name dataset.DataSetName = "PersonPet" ' Create tables for people and pets Dim people as DataTable = new DataTable("Person") Dim pets as DataTable = new DataTable("Pet") ' Set up the columns in the Tables Dim personname as DataColumn = new DataColumn ("Name", GetType (System.String)) Dim personAge as DataColumn = new DataColumn ("Age", GetType (System.Int32)) Dim petname as DataColumn = new DataColumn ("Name", GetType (System.String)) Dim pettype as DataColumn = new DataColumn ("Type", GetType (System.String)) ' Add columns to person table Dim id as DataColumn = people.Columns.Add("ID", GetType (System.Int32)) id.AutoIncrement = true Dim primarykey as DataColumn() = new DataColumn() {id} people.PrimaryKey = primarykey people.Columns.Add (personname) people.Columns.Add (personAge) ' Add columns to pet table id = pets.Columns.Add("ID", GetType (System.Int32)) id.AutoIncrement = true pets.PrimaryKey = new DataColumn() {id} id.AutoIncrement = true Dim ownerid as DataColumn = pets.Columns.Add("OwnerID", GetType (System.Int32)) Dim foreignkey as DataColumn() = new DataColumn() {ownerid} pets.Columns.Add (petname) pets.Columns.Add (pettype) ' Add tables to the DataSet dataset.Tables.Add (people) dataset.Tables.Add (pets) ' Add people Dim mark as DataRow = people.NewRow() mark(personname) = "Mark" mark(personAge) = 18 people.Rows.Add(mark) Dim william as DataRow = people.NewRow() william(personname) = "William" william(personAge) = 12 people.Rows.Add(william) Dim james as DataRow = people.NewRow() james(personname) = "James" james(personAge) = 19 people.Rows.Add(james) Dim levi as DataRow = people.NewRow() levi(personname) = "Levi" levi(personAge) = 4 people.Rows.Add(levi) ' Add relationships Console.WriteLine("Creating relationships between people and pets ...") Dim personpetrel as DataRelation = new DataRelation ("PersonPet", primarykey, foreignkey, false) dataset.Relations.Add (personpetrel) ' Add pets Dim row as DataRow = pets.NewRow() row("OwnerID") = mark("ID") row(petname) = "Frank" row(pettype) = "cat" pets.Rows.Add(row) row = pets.NewRow() row("OwnerID") = william("ID") row(petname) = "Rex" row(pettype) = "dog" pets.Rows.Add(row) row = pets.NewRow() row("OwnerID") = james("ID") row(petname) = "Cottontail" row(pettype) = "rabbit" pets.Rows.Add(row) row = pets.NewRow() row("OwnerID") = levi("ID") row(petname) = "Sid" row(pettype) = "snake" pets.Rows.Add(row) row = pets.NewRow() row("OwnerID") = levi("ID") row(petname) = "Tickles" row(pettype) = "spider" pets.Rows.Add(row) row = pets.NewRow() row("OwnerID") = william("ID") row(petname) = "Tweetie" row(pettype) = "canary" pets.Rows.Add(row) ' commit changes dataset.AcceptChanges() catch e as Exception Console.WriteLine ("Exception: {0}", e.ToString()) end try end sub |
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C# | VB |
DataSet 的 AcceptChanges 方法接受所有的更改,这些更改是自加载数据集以来或自上次调用 AcceptChanges 以来对数据集所做的更改。所有新的和修改过的行保持不变,移除已删除的行。有关其他 DataSet 关系方法的更多信息,请参阅如何获取 ADO.NET 的概述
为了将架构保存到文件,该示例调用 DataSet 的 WriteXmlSchema 方法,传递表示目标文件的 StreamWriter 类。
StreamWriter writer = null; try { Console.WriteLine("Writing the schema to {0} ...", mySaveSchema); writer = new StreamWriter(mySaveSchema); datadoc.DataSet.WriteXmlSchema(writer); } catch (Exception e) { Console.WriteLine("Exception: {0}", e.ToString()); } finally { if (writer != null) writer.Close(); } Dim writer as StreamWriter try Console.WriteLine("Writing the schema to {0} ...", mySaveSchema) writer = new StreamWriter(mySaveSchema) datadoc.DataSet.WriteXmlSchema(writer) catch e as Exception Console.WriteLine ("Exception: {0}", e.ToString()) finally If Not writer Is Nothing writer.Close() end if end try |
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C# | VB |
下列输出显示由 DisplayTables 方法在数据集中创建的表。有关 DisplayTables 方法的更多信息,请参阅如何从 XML 推导出数据集映射。该示例将推导出的架构写到 PersonPet.xsd 文件中。
Loading the DataSet ... Creating relationships between people and pets ... DataSet: PersonPet contains ... No of Tables: 2 Table content ... TableName = Person --------- Columns ... ID Name Age Number of rows = 4 Rows ... 0 Mark 18 1 William 12 2 James 19 3 Levi 4 TableName = Pet --------- Columns ... ID OwnerID Name Type Number of rows = 6 Rows ... 0 0 Frank cat 1 1 Rex dog 2 2 Cottontail rabbit 3 3 Sid snake 4 3 Tickles spider 5 1 Tweetie canary PersonPet Name = Mark owns Pet = Frank the cat Name = William owns Pet = Rex the dog Pet = Tweetie the canary Name = James owns Pet = Cottontail the rabbit Name = Levi owns Pet = Sid the snake Pet = Tickles the spider Writing the schema to PersonPet.xsd ...