c＃将DataGridView保存到Xml文件

Question

This is my button to save file:

private void metroButton12_Click(object sender, EventArgs e) // save
{
    DataSet ds = (DataSet)dataGridView1.DataSource;
    SaveFileDialog sfd = new SaveFileDialog();
    sfd.Filter = "XML|*.xml";
    if (sfd.ShowDialog() == DialogResult.OK)
    {
        try
        {
            ds.Tables[0].WriteXml(sfd.FileName);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex);
        }
    }
}

I try to safe my datagridview to XML but nothing happpend when I choose file. When I start console I see this: System.NullReferenceException: The object reference was not set to an object instance.

My gridview look like: ID Name 1 Michale 2 Noob

What am I doing here wrong?.. I saw a lot of thing's on the web but could not find any solutions in stackoverflow and other forums. Please be patient for newbie guys. Thank you!

Answer 1

To me it sounds like your problem is not where you think it is.

when i start console i see this : System.NullReferenceException: The object reference was not set to an object instance.

To me you are implying that you get the message when you launch the application, not when you click the button. If you get the error before you click, your problem is elsewhere and not in the code snippet you posted. Here is a complete and testable snippet of what you are currently doing.

using System;
using System.Data;
using System.Windows.Forms;

namespace DataGridViewToXML_43053387
{
    public partial class Form1 : Form
    {
        //DataSet theDataSet;
        public Form1()
        {
            InitializeComponent();
            InsertDgvIntoForm();
            ExportDgvToXML();
        }

        private void InsertDgvIntoForm()
        {
            //create a data set
            DataSet ds = new DataSet();
            //create a data table for the data set
            DataTable dt = new DataTable();
            //create some columns for the datatable
            DataColumn dc = new DataColumn("ItemName");
            DataColumn dc2 = new DataColumn("ItemValue");
            DataColumn dc3 = new DataColumn("Blah");
            DataColumn dc4 = new DataColumn("Bleh");
            //add the columns to the datatable
            dt.Columns.Add(dc);
            dt.Columns.Add(dc2);
            dt.Columns.Add(dc3);
            dt.Columns.Add(dc4);

            //create 5 rows of irrelevant information
            for (int i = 0; i < 5; i++)
            {
                DataRow dr = dt.NewRow();
                dr["ItemName"] = "Item" + i + "Name";
                dr["ItemValue"] = "Item" + i + "Value";
                dr["Blah"] = "Item" + i + "Blah";
                dr["Bleh"] = "Item" + i + "Bleh";
                dt.Rows.Add(dr);
            }
            //add the datatable to the datasource
            ds.Tables.Add(dt);
            //just because it looks better on my screen
            dataGridView1.AutoSize = true;
            //make this data the datasource of our gridview
            dataGridView1.DataSource = ds.Tables[0];

        }

        private void ExportDgvToXML()
        {
            DataTable dt = (DataTable)dataGridView1.DataSource;
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.Filter = "XML|*.xml";
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    dt.WriteXml(sfd.FileName);
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex);
                }
            }
        }
    }
}

Answer 2

blaze_125 answer didn't help me so I've found this solution:

private void btnXML_Save_Click(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.TableName = "Bank";

    for (int i = 0; i < dataGridView1.Columns.Count; i++)
    {
        //if (dataGridView1.Columns[i].Visible) // Add's only Visible columns (if you need it)
        //{
            string headerText = dataGridView1.Columns[i].HeaderText;
            headerText = Regex.Replace(headerText, "[-/, ]", "_");

            DataColumn column = new DataColumn(headerText);
            dt.Columns.Add(column);
        //}
    }

    foreach (DataGridViewRow DataGVRow in dataGridView1.Rows)
    {
        DataRow dataRow = dt.NewRow();
        // Add's only the columns that you want
        dataRow["BLZ"] = DataGVRow.Cells["BLZ"].Value;
        dataRow["Test_1"] = DataGVRow.Cells["Test 1"].Value;
        dataRow["Test_2"] = DataGVRow.Cells["Test-2"].Value;
        dataRow["PIN_TAN_Test_URL"] = DataGVRow.Cells["PIN/TAN-Test URL"].Value;

        dt.Rows.Add(dataRow); //dt.Columns.Add();
    }
    DataSet ds = new DataSet();
    ds.Tables.Add(dt);

    //Finally the save part:
    XmlTextWriter xmlSave = new XmlTextWriter(XML_Save_Path_Filename, Encoding.UTF8);
    xmlSave.Formatting = Formatting.Indented;
    ds.DataSetName = "Data";
    ds.WriteXml(xmlSave);
    xmlSave.Close();
}

Result will look like this:

<Data>
  <Bank>
    <BLZ>10000001</BLZ>
    <Test_1>server.bank.com</Test_1>
    <Test_2>V3.0</Test_2>
    <PIN_TAN_Test_URL>https://test.bank.com/</PIN_TAN_Test_URL>
  </Bank>
  ....
  <Bank>
    <BLZ>12396123</BLZ>
    <HBCI_Zugang_DNS>test01.test.com</HBCI_Zugang_DNS>
    <HBCI_Version>V3.0</HBCI_Version>
    <PIN_TAN_Test_URL>https://test11.test.com</PIN_TAN_Test_URL>
  </Bank>
</Data>