XML和关系数据----将数据集映射保存到XSD架构文件
如何将数据集映射保存到 XSD 架构文件
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);
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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());
}
}
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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();
}
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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 ...
摘要
- WriteXmlSchema 方法将数据集中的关系数据的内部结构映射保存为 XSD 架构。
- XmlDataDocument 的 DataSet 属性使您能够相关地查看和管理 XML 文档中的结构化数据
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