how to insert null value into database through text boxes

Question

i have 3 text boxes for insert data into database but out of 3 text boxes only two textboxes to be used for insert data ,and 3 rd text box must be empty but in database it should shows null. i wrote some code  but display a error like syntax error near ','

Wim Sturkenboom · Answer

[quote]
i wrote some code  but display a error like syntax error near ','
[/quote]
show the relevant code and show the exact error message
And you probably need to use DBNull instead of null to achieve this from C#.

Michal Habalcik · Answer

you should do something like:
If (String.IsNullOrEmpty(textbox.Text)) {
INSERT INTO some_table (column1, column2, column3) VALUES (@tb1, @tb2, NULL)
}
else
{
INSERT INTO some_table (column1, column2, column3) VALUES (@tb1, @tb2,  textbox.Text )
}
or even a more simple version:
INSERT INTO some_table (column1, column2, column3) VALUES (@tb1, @tb2,  String.IsNullOrEmpty(textbox.Text) ? NULL : textbox.Text )

Vulpes · Answer

I'd have thought that, for SQL Server at least, something like this should work :
INSERT INTO some_table (column1, column2, column3) VALUES (@tb1, @tb2, NULL)
where tb1 and tb2 are parameters whose values are (or are based on) textbox1 and textbox2 respectively.