how to get the xmlfile content from database

Hi, you need to use a component spire.dataexport for .net to complete the process. And here is a tutorial article that exports datatable to xml file, check it.
http://www.e-iceblue.com/Knowledgebase/Spire.DataExport/Spire.DataExport-Program-Guide/How-to-Export-Data-into-XML-in-C.html

Below is the sample code:
private void Form1_Load(object sender, EventArgs e)
{
oleDbConnection1.ConnectionString = txtConnectString.Text;
oleDbCommand1.CommandText = txtCommandText.Text;
using (OleDbDataAdapter da = new OleDbDataAdapter())
{
da.SelectCommand = oleDbCommand1;
da.SelectCommand.Connection = oleDbConnection1;
DataTable dt = new DataTable();
da.Fill(dt);
dataGridView1.DataSource = dt;
}
}
private void btnExportToXml_Click(object sender, EventArgs e)
{
Spire.DataExport.XML.XMLExport xmlExport = new Spire.DataExport.XML.XMLExport();
xmlExport.DataSource = Spire.DataExport.Common.ExportSource.DataTable;
xmlExport.DataTable = this.dataGridView1.DataSource as DataTable;
xmlExport.ActionAfterExport = Spire.DataExport.Common.ActionType.OpenView;
xmlExport.FileName = @"..\..\ToXml.xml";
xmlExport.SaveToFile();
}
DEMO: http://www.e-iceblue.com/downloads/demo/spire.dataexport/introduction/ToXml.zip
hope it helps.