I get the message "Object reference not set to an instance of an object" when clearing a data table.
Ds.tables["table_name"].Clear();
The datatable exists and it contains data.
Thanks for your help.
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`tables["table_name"]` resolves to null, so you cant call `Clear()` on it – maccettura Sep 12 '18 at 17:01
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3Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) – Dour High Arch Sep 12 '18 at 17:05
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`Ds?.tables["table_name"]?.Clear();` – Lews Therin Sep 12 '18 at 17:13
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Instead of shotgunning null checks all over your code, find out what is null and fix it. – Dour High Arch Sep 12 '18 at 17:21
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Did you try the [debugger](https://msdn.microsoft.com/en-us/library/y740d9d3.aspx), your very best friend in the world of coding. – TaW Sep 12 '18 at 17:32
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Of course i used it but still can't find the source of the problem. – user9095135 Sep 13 '18 at 08:36
2 Answers
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It's about your object not database, you need to check Ds and then Ds.tables["table_name"] to if they are null then call Ds.tables["table_name"].clear();
Sina
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Add condition
if(Ds.tables["table_name"]!=null){
Ds.tables["table_name"].Clear();
}
OR
if(Ds.tables["table_name"]!=null){
Ds.Rows.Clear();
}
Ashfaque Ali Solangi
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I added the condition and it passes, it's not null. And the rows.clear() did not work. – user9095135 Sep 12 '18 at 17:13
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can you check the number of rows present in (Ds.tables["table_name"].Rows.Count) – Ashfaque Ali Solangi Sep 12 '18 at 17:25
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I can see the number of rows using the debugger. It contains 5 rows. – user9095135 Sep 12 '18 at 17:55
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I forgot to mention that the datatable is cleared even if it shows the error msg. The programme does not stop it keeps running. – user9095135 Sep 12 '18 at 18:03
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then i think its not related with Ds.tables["table_name"] maybe something wrong in app code? or just for a try set it null manually inside if condition "Ds.tables["table_name"] = null;" and try – Ashfaque Ali Solangi Sep 12 '18 at 21:13