Object reference not set to an instance of an object IN c# export csv

Question

I designed a form to import and export into database then I used this code to export table into csv button

but it always gives me that I have a problem inside the foreach "Object reference not set to an instance of an object"

        private void button5_Click(object sender, EventArgs e) 
    {
//Build the CSV file data as a Comma separated string.
string csv = string.Empty;

//Add the Header row for CSV file.
foreach (DataGridViewColumn column in dataGridView1.Columns)
{
    csv += column.HeaderText + ',';
}

//Add new line.
csv += "\r\n";

//Adding the Rows
foreach (DataGridViewRow row in dataGridView1.Rows)
{
    foreach (DataGridViewCell cell in row.Cells)
    {
        //Add the Data rows.
        csv += cell.Value.ToString().Replace(",", ";") + ',';
    }

    //Add new line.
    csv += "\r\n";
}

//Exporting to CSV.
string folderPath = "C:\\CSV\\";
File.WriteAllText(folderPath + "DataGridViewExport.csv", csv);

}

MutantNinjaCodeMonkey · Answer 1 · 2015-12-24T19:28:05.200

1

Odds are, one of the cell's values is null. Performing a ToString() call on a null object will throw that exception. This might work instead:

foreach (DataGridViewCell cell in row.Cells)
{
    object csvValue = (cell == null || cell.Value == null) ? string.Empty : cell.Value;
    //Add the Data rows.
    csv += csvValue.ToString().Replace(",", ";") + ',';
}

edited Dec 24 '15 at 19:28

answered Dec 24 '15 at 18:45

MutantNinjaCodeMonkey

1,189
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thank you but there is a debugging problem now – Alex Gu Dec 24 '15 at 19:06
Probably need to elaborate a little more about that if you're looking for assistance. :) – MutantNinjaCodeMonkey Dec 24 '15 at 19:09
Error 1 Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?) – Alex Gu Dec 24 '15 at 19:12
ah.. see my edit. Change the type to `object` for the csvValue variable. – MutantNinjaCodeMonkey Dec 24 '15 at 19:14
now the same problem Object reference not set to an instance of an object – Alex Gu Dec 24 '15 at 19:26
Hmm.. That probably means that cell itself is null. I just modified the code to check for that. I'm not sure why you'd get null Cells though. – MutantNinjaCodeMonkey Dec 24 '15 at 19:30
it fixed but now this problem Could not find a part of the path 'C:\CSV\DataGridViewExport.csv' – Alex Gu Dec 24 '15 at 19:44
This is starting to venture out of the scope of your original question. But I'd check to see if you've made a folder for "C:\CSV". The `Directory` object should provide methods to check if `folderPath` exists, as well methods to create it before you write the file to that path. – MutantNinjaCodeMonkey Dec 24 '15 at 19:50

Object reference not set to an instance of an object IN c# export csv

1 Answers1