How save txt file if third column datagridview is empty

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Hello

i have a datagridview.
I save the data of 3 columns in a txt file.
The third column is entered text by user.
then I save the data in a txt file.
So far so good.
But if some one leaves the third column empty.
then I still want to save the file.
but then i get an error from the compiler.
System.NullReferenceException
I think I should apply an exception but I don't know how.
Please help

What I have tried:

C#

TextWriter sw = new StreamWriter(@"C:\folder\Test.txt", true);
                int rowcount = dataGridView1.Rows.Count;
                for (int i = 0; i < rowcount - 0; i++)
                {
                    sw.WriteLine(dataGridView1.Rows[i].Cells[1].Value.ToString() + "\t"
                                 + dataGridView1.Rows[i].Cells[2].Value.ToString() + "\t"
                                   + dataGridView1.Rows[i].Cells[4].Value.ToString() + "\t");
                }
                sw.Close();
                MessageBox.Show("FILE SAVED");

Posted 15-Nov-21 14:37pm

Member 14270871

Updated 24-Nov-21 8:47am

Wendelius

v2

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3 solutions

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Wendelius · Answer 1 · 2021-11-15T16:03:00

Taken you use C# 6 or later you can try using Null-conditional operator. For example if the cell itself is null

C#

sw.WriteLine(dataGridView1.Rows[i].Cells[1]?.Value.ToString() + "\t"
+ dataGridView1.Rows[i].Cells[2]?.Value.ToString() + "\t"
+ dataGridView1.Rows[i].Cells[4]?.Value.ToString() + "\t");

or if the value in an existing cell is null

C#

sw.WriteLine(dataGridView1.Rows[i].Cells[1].Value?.ToString() + "\t"
+ dataGridView1.Rows[i].Cells[2].Value?.ToString() + "\t"
+ dataGridView1.Rows[i].Cells[4].Value?.ToString() + "\t");

For more information, see Member access operators and expressions - C# reference | Microsoft Docs[^]

BillWoodruff · Answer 2 · 2021-11-15T17:06:00

hypotheses:

1) there is no Column #4: but, if that were true, you'd get an IndexOutOfRange error.

2) the ColumnType of Column #4 is not a standard (TextBox, Button, etc.) ColumnType, but, a custom Control. however, you imply that the user can edit that Column. is #4 a custom Column ? if yes, it needs a ToString implementation that will avoid failure trying to convert null.

so, having ruled out the most likely scenarios, you need to:

1) describe the versions of Visual Studio and C#/FrameWork you are using.

2) is the DataGridView the standard one provided in WinForms ?

TRY this with your DataGridView and look at the output:

when i want to debug a DataGridView, or build a string representation of all its rows/columns/values, i use this:

public string DGVToString(DataGridView dgv)
{
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < dataGridView1.Rows.Count; i++)
    {
        sb.AppendLine($"Row: {i}");

        for (int j = 0; j < dataGridView1.Columns.Count; j++)
        {
            sb.Append($"Column: {j}\t");
            var value = dataGridView1.Rows[i].Cells[j].Value;

            // using older .NET versions
            value = value == null ? "null" : value.ToString();

            // using newer .NET versions
            // value ??= "null";

            sb.Append($"value: {value}");
            sb.Append("\t");
        }

        sb.AppendLine();
    }

    return sb.ToString();
}

// to save the data:
// using (TextWriter sw = new StreamWriter(@"C:\folder\Test.txt", true", true))
// {
//    sw.WriteLine(DGVToString(dataGridView1));
//    sw.Close();
// }

Note the use of StringBuilder to reduce the number of string allocations and build the output faster. Note the test for 'null that avoids an error when ToString is called on a null vak=lue

Richard Deeming · Answer 3 · 2021-11-17T00:20:00

Solution 3

You're already using a TextWriter, so the simplest solution would be:

C#

using (TextWriter sw = File.AppendText(@"C:\folder\Test.txt"))
{
    foreach (DataGridViewRow row in dataGridView1.Rows)
    {
        sw.Write(row.Cells[1].Value);
        sw.Write('\t');
        sw.Write(row.Cells[2].Value);
        sw.Write('\t');
        sw.Write(row.Cells[3].Value);
        sw.WriteLine();
    }
}

MessageBox.Show("FILE SAVED");

Posted 17-Nov-21 0:20am

Richard Deeming

Updated 17-Nov-21 1:05am

v2

Comments

[no name] 17-Nov-21 7:04am

HiIf use you code.
I cat error Compiler Error CS1061

Richard Deeming 17-Nov-21 7:06am

Try replacing var row in ... with DataGridViewRow row in ....

If that doesn't work, you'll need to specify which line the error is pointing to.

[no name] 17-Nov-21 7:22am

Hello
this works.
Is it also possible if one row and the last cell is empty lets say cell[3]
that this line will not save and the rest will
Thanks in advice

Richard Deeming 17-Nov-21 7:24am

Yes; just add a check within the foreach loop. For example:

foreach (DataGridViewRow row in dataGridView1.Rows)
{
    object value = row.Cells[3].Value;
    if (value is null || string.IsNullOrEmpty(Convert.ToString(value))) continue;
    
    sw.Write(row.Cells[1].Value);
    sw.Write('\t');
    sw.Write(row.Cells[2].Value);
    sw.Write('\t');
    sw.Write(value);
    sw.WriteLine();
}

[no name] 17-Nov-21 7:30am

Thanks
This works

[no name] 23-Nov-21 12:12pm

Hello Richard
The code that you suggested woks wel fo me.
I just have one more question.
is it also possible that if the line already exists in the saved file.
That this one not wil be saved.
Like you dit with the empty cell.
Regards

How save txt file if third column datagridview is empty

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