初学,如何将数据输出为固定格式的xml？

Question

从数据库中返回xml数据，主流的dbms都有api提供，如sqlserver的openxml,for xml，oracle的xmlquery等，也提供了xml数据格式控制的语法，具体可以参考api的语法说明
如果你的应用对xml格式的要求比较高，如要使用.net的xml序列化，那么可以使用xsl对数据库返回的xml数据做一部格式转换，就可以满足通用性的需求，当然数据大的话性能损失那是相当严重，因此dal的设计就要考虑了

Answer 1

这里提供一个使用 System.Xml.XmlWriter 手动输出 XML Demo, XmlWriter/XmlReader 效率比较高，当然你还可以使用 XmlDocument, XmlPathNavigator 等等参考示例:// 输出XML
void CreateProductCategoryXml3()
    {
        DataSet ds = CreateProductCategoryDataSet();
        DataTable dtPro = ds.Tables["Products"];
        DataTable dtCat = ds.Tables["Categories"];        string filePath = Server.MapPath(@"..\..\App_Data\ProductCategory3.Xml");
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;        using (XmlWriter writer = XmlWriter.Create(filePath, settings)) {
            writer.WriteStartElement(ds.DataSetName);            //writer.WriteStartElement(dtCat.TableName);
            foreach (DataRow catRow in dtCat.Rows) {
                writer.WriteStartElement("Category");                writer.WriteStartAttribute(dtCat.Columns[0].ColumnName);
                writer.WriteString(catRow[0].ToString());                writer.WriteStartAttribute(dtCat.Columns[1].ColumnName);
                writer.WriteString(catRow[1].ToString());
                writer.WriteEndAttribute();                //writer.WriteStartElement(dtPro.TableName);
                foreach (DataRow proRow in catRow.GetChildRows(ds.Relations[0])) {
                    writer.WriteStartElement("Product");                    writer.WriteStartAttribute(dtPro.Columns[0].ColumnName);
                    writer.WriteString(proRow[0].ToString());                    writer.WriteStartAttribute(dtPro.Columns[1].ColumnName);
                    writer.WriteString(proRow[1].ToString());
                    writer.WriteEndAttribute();                    writer.WriteEndElement();
                }
                //writer.WriteEndElement();                writer.WriteEndElement();
            }
            //writer.WriteEndElement();            writer.WriteEndElement();
        }
    }// 提供测试数据
public static DataSet CreateProductCategoryDataSet()
    {
        DataSet ds = new DataSet("ProductCategorySet");
        DataTable dtPro = CreateProductTable();
        DataTable dtCat = CreateCategoryTable();
        ds.Tables.Add(dtPro);
        ds.Tables.Add(dtCat);
        ds.Relations.Add(dtCat.Columns["CategoryID"], dtPro.Columns["CategoryID"]);
        
        return ds;
    }    public static DataTable CreateProductTable()
    {
        DataTable tbl = new DataTable("Products");        tbl.Columns.Add("ProductID", typeof(int));
        tbl.Columns.Add("ProductName", typeof(string));        
        tbl.Columns.Add("CategoryID", typeof(int));
        tbl.Columns.Add("DateCreated", typeof(DateTime));
        DataRow row = tbl.NewRow();
        row[0] = 1;
        row[1] = "Chai";
        row[2] = 1;
        row["DateCreated"] = new DateTime(1999, 3, 24);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 2;
        row[1] = "Chang";
        row[2] = 1;
        row[3] = new DateTime(1999, 4, 2);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 3;
        row[1] = "Aniseed Syrup";
        row[2] = 2;
        row[3] = new DateTime(1999, 3, 24);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 4;
        row[1] = "Chef Anton's Cajun Seasoning";
        row[2] = 2;
        row[3] = new DateTime(2000, 12, 12);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 5;
        row[1] = "Chef Anton's Gumbo Mix";
        row[2] = 2;
        row[3] = new DateTime(2000, 12, 25);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 47;
        row[1] = "Zaanse koeken";
        row[2] = 3;
        row[3] = new DateTime(2001, 1, 2);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 48;
        row[1] = "Chocolade";
        row[2] = 3;
        row[3] = new DateTime(2001, 1, 12);
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 49;
        row[1] = "Maxilaku";
        row[2] = 3;
        row[3] = new DateTime(2001, 8, 12);
        tbl.Rows.Add(row);        return tbl;
    }    public static DataTable CreateCategoryTable()
    {
        DataTable tbl = new DataTable("Categories");        tbl.Columns.Add("CategoryID", typeof(int));
        tbl.Columns.Add("CategoryName", typeof(string));        
        DataRow row = tbl.NewRow();
        row[0] = 1;
        row[1] = "Beverages";
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 2;
        row[1] = "Condiments";        
        tbl.Rows.Add(row);        row = tbl.NewRow();
        row[0] = 3;
        row[1] = "Confections";
        tbl.Rows.Add(row);        return tbl;
    }4. 
结果示例<?xml version="1.0" encoding="utf-8"?>
<ProductCategorySet>
  <Category CategoryID="1" CategoryName="Beverages">
    <Product ProductID="1" ProductName="Chai" />
    <Product ProductID="2" ProductName="Chang" />
  </Category>
  <Category CategoryID="2" CategoryName="Condiments">
    <Product ProductID="3" ProductName="Aniseed Syrup" />
    <Product ProductID="4" ProductName="Chef Anton's Cajun Seasoning" />
    <Product ProductID="5" ProductName="Chef Anton's Gumbo Mix" />
  </Category>
  <Category CategoryID="3" CategoryName="Confections">
    <Product ProductID="47" ProductName="Zaanse koeken" />
    <Product ProductID="48" ProductName="Chocolade" />
    <Product ProductID="49" ProductName="Maxilaku" />
  </Category>
</ProductCategorySet>
Good Luck1