Appending in an existing xml file using dataset

问题:

I made this code but it has a problem that everytime i run it ..it overwrites my xml file and nothing new is added this is my xml file:

- <DATA>
- <Users>
  <MonopolyID>User2</MonopolyID> 
  <Password>pass2</Password> 
  <FirstName>User2Name</FirstName> 
  <LastName>User2LastName</LastName> 
  </Users>
  </DATA>

u can see that user1 was overwritten anyway this is my code:

public partial class SignUpPage : Form
    {
private void button1_Click(object sender, EventArgs e)
        {
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            DataColumn dc = new DataColumn("MonopolyID", typeof(string));
            dt.Columns.Add(dc);
            dc = new DataColumn("Password", typeof(string));
            dt.Columns.Add(dc);
            dc = new DataColumn("FirstName", typeof(string));
            dt.Columns.Add(dc);
            dc = new DataColumn("LastName", typeof(string));
            dt.Columns.Add(dc);
            DataRow dr = dt.NewRow();
            dt.Rows.Add(textBox3.Text, textBox4.Text, textBox1.Text, textBox2.Text);//here just putting  the texts in the texts box for the first row
            dt.TableName = "Users";
            ds.Tables.Add(dt);
            ds.DataSetName = "DATA";
            ds.WriteXml(@"pathOfTheFile..");
    }
}

回答1:

You need to use 'ds.Merge(dt);' like below example:

protected void Button1_Click(object sender, EventArgs e)
    {
        DataSet ds = new DataSet();
        ds.ReadXml(Server.MapPath("~/xmldata.xml"));
        DataTable dt = new DataTable();
        DataColumn dc = new DataColumn("MonopolyID", typeof(string));
        dt.Columns.Add(dc);
        dc = new DataColumn("Password", typeof(string));
        dt.Columns.Add(dc);
        dc = new DataColumn("FirstName", typeof(string));
        dt.Columns.Add(dc);
        dc = new DataColumn("LastName", typeof(string));
        dt.Columns.Add(dc);
        DataRow dr = dt.NewRow();
        dt.Rows.Add("User3", "pass3", "User3Name", "User3LastName");
        //dt.TableName = "Users";
        ds.Tables.Add(dt);
        //ds.DataSetName = "DATA";
        ds.Merge(dt);
        ds.WriteXml(Server.MapPath("~/xmldata.xml"));
    }

And so far generated below xml file

<?xml version="1.0" standalone="yes"?>
<NewDataSet>
  <Table1>
    <MonopolyID>User1</MonopolyID>
    <Password>pass1</Password>
    <FirstName>User1Name</FirstName>
    <LastName>User1LastName</LastName>
  </Table1>
  <Table2>
    <MonopolyID>User2</MonopolyID>
    <Password>pass2</Password>
    <FirstName>User2Name</FirstName>
    <LastName>User2LastName</LastName>
  </Table2>
  <Table3>
    <MonopolyID>User3</MonopolyID>
    <Password>pass3</Password>
    <FirstName>User3Name</FirstName>
    <LastName>User3LastName</LastName>
  </Table3>
</NewDataSet>

Let me know if that helps.