How to filter XML file from combo box selection

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C#

XML

C#4.0

Hi i need to display data in this format to a datagridview. my datasource is XML.
I want to filter the xml file according to the combobox selection.
I have a confusion that whether i am using proper logic for generating data.

please guide me if there is better way to design the xml file.
And one more is it possible to update the xml file from the datagridview
like we do in dataadapter.Update(ds)

<big></big>
        ITEM            X     Y
	amount	          150	210
	amountword	      150	210
	date	          400	250
	payagainst	       30	180

i am using dataset for generating xml
my code is

private void button1_Click(object sender, EventArgs e)
       {
           DataTable dt = new DataTable();
           dt.TableName = "Bank";
           DataColumn dc = new DataColumn("BankName");
           DataColumn dc0 = new DataColumn("item");
           DataColumn dc1 = new DataColumn("X");
           DataColumn dc2 = new DataColumn("Y");
          dt.Columns.Add(dc);
           dt.Columns.Add(dc0);
           dt.Columns.Add(dc1);
           dt.Columns.Add(dc2);
           dt.Rows.Add("xyz","amount", "150", "210");
           dt.Rows.Add("xyz", "amountword", "150", "210");
           dt.Rows.Add("xyz", "date", "400", "250");
           dt.Rows.Add("xyz", "payagainst", "30", "180");

           dt.Rows.Add("abc", "amount", "180", "210");
           dt.Rows.Add("abc", "amountword", "50", "20");
           dt.Rows.Add("abc", "date", "40", "20");
           dt.Rows.Add("abc", "payagainst", "3", "18");
           DataSet ds = new DataSet();
           ds.DataSetName = "chequesettings";
           ds.Tables.Add(dt);
           ds.WriteXml("chequesettings.xml");
           MessageBox.Show("Xml file created sucessfully");
       }

DataSet ds = new DataSet();
           ds.ReadXml("chequesettings.xml");
           dataGridView1.DataSource=ds.Tables[0];

<chequesettings>
  <Bank>
    <BankName>xyz</BankName>
    <item>amount</item>
    <X>150</X>
    <Y>210</Y>
  </Bank>
  <Bank>
    <BankName>xyz</BankName>
    <item>amountword</item>
    <X>150</X>
    <Y>210</Y>
  </Bank>
  <Bank>
    <BankName>xyz</BankName>
    <item>date</item>
    <X>400</X>
    <Y>250</Y>
  </Bank>
  <Bank>
    <BankName>xyz</BankName>
    <item>payagainst</item>
    <X>30</X>
    <Y>180</Y>
  </Bank>
  <Bank>
    <BankName>abc</BankName>
    <item>amount</item>
    <X>180</X>
    <Y>210</Y>
  </Bank>
  <Bank>
    <BankName>abc</BankName>
    <item>amountword</item>
    <X>50</X>
    <Y>20</Y>
  </Bank>
  <Bank>
    <BankName>abc</BankName>
    <item>date</item>
    <X>40</X>
    <Y>20</Y>
  </Bank>
  <Bank>
    <BankName>abc</BankName>
    <item>payagainst</item>
    <X>3</X>
    <Y>18</Y>
  </Bank>
</chequesettings>