“Multiple” XML-File (new input should not replace) using c#

Question

I'm writing a short program which displays me all my To Do's. I got 2 tabs. 1 Tab is for create a new To Do and the other tab is for displaying me the details of every To Do I selected. So I have to save the created To Do's in a xml file. For this I am using DataTable and DataSet and it works fine. Here my code:

DataTable datatable = new DataTable();
            datatable.TableName = "SaveInput";

            DataColumn dc1 = new DataColumn("Name");
            DataColumn dc2 = new DataColumn("Priority");
            DataColumn dc3 = new DataColumn("StartDate");
            DataColumn dc4 = new DataColumn("EndDateSoll");
            DataColumn dc5 = new DataColumn("EndDateIst");
            DataColumn dc6 = new DataColumn("Comment");

            datatable.Columns.Add(dc1);
            datatable.Columns.Add(dc2);
            datatable.Columns.Add(dc3);
            datatable.Columns.Add(dc4);
            datatable.Columns.Add(dc5);
            datatable.Columns.Add(dc6);

            datatable.Rows.Add(txt_Name.Text, combox_Priority.Text, txt_Beginn.Text, txt_EndSoll.Text, txt_EndIst.Text, txt_Bemerkungen.Text);

            DataSet dataset = new DataSet();

            dataset.Tables.Add(datatable);
            dataset.DataSetName = "MyProgram";

            dataset.WriteXml(@"C:\Users\rs\Desktop\Test\save.xml");

But my problem now is: If I create a new "To Do" in tab1, it replace the new "To Do" in the .xml file. So if I have a look at the .xml file, there is still 1 "To Do". I just want to write more tables in the .xml file. So my .xml file looks like this:

<MyProgram>
  <SaveInput>
    <Name>todo1</Name>
    <Priority>high</Priority>
    <StartDate>today</StartDate>
    <EndDateSoll>later</EndDateSoll>
    <EndDateIst>not finished</EndDateIst>
    <Comment>blabla</Comment>
  </SaveInput>
</MyProgram>

But it should look like this for example:

<MyProgram>
  <SaveInput>
    <Name>todo1</Name>
    <Priority>high</Priority>
    <StartDate>today</StartDate>
    <EndDateSoll>later</EndDateSoll>
    <EndDateIst>not finished</EndDateIst>
    <Comment>blabla</Comment>

    <Name>todo2</Name>
    <Priority>high</Priority>
    <StartDate>yesterday</StartDate>
    <EndDateSoll>tomorrow</EndDateSoll>
    <EndDateIst>not finished</EndDateIst>
    <Comment>testtest</Comment>
  </SaveInput>
</MyProgram>

I hope someone can help me or give me a hint so I can create more than 1 To-Do.

Cheers

EDIT: It's a WinForm Application

Answer 1

This code should work for you.

Check it out

DataSet ds = new DataSet();
            if (File.Exists(@"C:\Users\rs\Desktop\Test\save.xml"))
            {
                ds.ReadXml(@"C:\Users\rs\Desktop\Test\save.xml");

                ds.Tables[0].Rows.Add(txt_Name.Text, combox_Priority.Text, txt_Beginn.Text, txt_EndSoll.Text, txt_EndIst.Text, txt_Bemerkungen.Text);
                ds.WriteXml(@"C:\Users\rs\Desktop\Test\save.xml");
            }
            else
            {
                DataTable datatable = new DataTable();
                datatable.TableName = "SaveInput";

                DataColumn dc1 = new DataColumn("Name");
                DataColumn dc2 = new DataColumn("Priority");
                DataColumn dc3 = new DataColumn("StartDate");
                DataColumn dc4 = new DataColumn("EndDateSoll");
                DataColumn dc5 = new DataColumn("EndDateIst");
                DataColumn dc6 = new DataColumn("Comment");

                datatable.Columns.Add(dc1);
                datatable.Columns.Add(dc2);
                datatable.Columns.Add(dc3);
                datatable.Columns.Add(dc4);
                datatable.Columns.Add(dc5);
                datatable.Columns.Add(dc6);

                datatable.Rows.Add(txt_Name.Text, combox_Priority.Text, txt_Beginn.Text, txt_EndSoll.Text, txt_EndIst.Text, txt_Bemerkungen.Text);

                DataSet dataset = new DataSet();

                dataset.Tables.Add(datatable);
                dataset.DataSetName = "MyProgram";

                dataset.WriteXml(@"C:\Users\rs\Desktop\Test\save.xml");
            }

Answer 2

Correct me if I'm wrong, but from your code it seems to me that you always create a new dataset, that contains only the new values. Do you read the already existing Todos first? If not, you simply always overwrite your xml file and the previous entries.