How to rows dynamically in datagrid C# wpf?

Question

I want to set number of rows of datagrid equal to a number given by user in a textbox. means if i enter 6 in the textbox, it should add 6 rows in the datagrid. thats what i want. I may be wrong. But Null exception is being thrown. How to fix my issue?

Here is the code:

          DataTable dt;
          DataRow dr;
        int rownumber=0;
        dt = new DataTable("emp2");
        DataColumn dc3 = new DataColumn("Wi", typeof(double));
        DataColumn dc4 = new DataColumn("Hi", typeof(double));

        rownumber = Int32.Parse(txtBexNumber.Text);
        dr[rownumber] = dt.NewRow();
        dt.Rows.Add(dr);
        dt.Columns.Add(dc3);
        dt.Columns.Add(dc4);

        datagrid1.ItemsSource = dt.DefaultView;

On which line exactly? Did you debug your code? Related: [What is a `NullReferenceException` and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Soner Gönül, Apr 20 '15 at 14:19
yeah i already did it. Made thorough search. after all searching and scratching i end up asking you people — Vanadium90, Apr 20 '15 at 14:22
what are you expecting 'dr[rownumber] = dt.NewRow();' to do? At that point dr hasn't been initialised so wouldn't have a property of '[rownumber]' — Dominic Scanlan, Apr 20 '15 at 14:32
I am expecting it to add that much number of rows. . means if i enter 6 in the textbox, it should add 6 rows. thats what i want. I may be wrong. — Vanadium90, Apr 20 '15 at 14:36

Rachel · Accepted Answer · 2015-04-20T14:37:19.060

3

You're creating a DataTable, then trying to immediately access a user-specified row in the table even though no rows have been added yet.

Use a loop to add rows first

for(int i = 0; i < rowNumber; i++)
{
    dr = dt.NewRow();
    dt.Rows.Add(dr);
}

As a side note, when working with WPF its easier to work with an ObservableCollection of objects instead of DataTables and DataRows. The data is much easier to understand and work with instead of trying to use DataRows and DataColumns.

var data = new ObservableCollection<MyObject>();

for (int i = 0; i < rowNumber; i++)
    data.Add(new MyObject() { Wi = 0, Hi = 0 });

dataGrid1.ItemsSource = data;

edited Apr 20 '15 at 14:37

answered Apr 20 '15 at 14:33

Rachel

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Nice to see your back on WPF – Failed Scientist Apr 20 '15 at 14:35
1

@TalhaIrfan :) I didn't go anywhere, I just got busy and don't have as much time for SO. Thanks though! – Rachel Apr 20 '15 at 14:38
Thank you so much for still finding some time for SO. We are grateful for any time you give here :) – Failed Scientist Apr 20 '15 at 14:41

score 0 · Answer 2 · answered Apr 20 '15 at 14:29

I guess it´s better to use

Int32.TryParse(txtBexNumber.Text, out rownumber);

(maybe you get the error for parsing an empty string? If possible try to debug where exactly the null pointer exception accurs)

Also validate if

dr[rownumber] = dt.NewRow();

works as expected. If e.g. dr[10] doesn´t exist, you get an exception.

How to rows dynamically in datagrid C# wpf?

2 Answers2