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I have a connection but it throws an error:

baglanti = new DataRelation("baglan",
                     ds.Tables["tblDeneme"].Columns["KategoriID"], 
                     ds.Tables["tblDeneme"].Columns["AltKategoriID"]);

Error:

An unhandled exception of type 'System.NullReferenceException' occurred in WindowsFormsApplication1.exe

marc_s
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kenankomurcu
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    Mmm Multi Dot statement.. Break it down into multiple variables, and debug it to know what is exactly generating null. Maybe TableName, maybe ColumnName.. We can't tell, this is guess work. – Zein Makki Dec 22 '16 at 07:27
  • Possible duplicate of [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) – Tetsuya Yamamoto Dec 22 '16 at 09:54

1 Answers1

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var a =  ds.Tables["tblDeneme"].Columns["KategoriID"];
var b =  ds.Tables["tblDeneme"].Columns["AltKategoriID"];
baglanti = new DataRelation("baglan",
                     ds.Tables["tblDeneme"].Columns["KategoriID"], 
                     ds.Tables["tblDeneme"].Columns["AltKategoriID"]);

Try this and debug your code, starting from var a.

You are probably getting some dbnull values while retrieving data from your dataset.

if (ds.Tables["tblDeneme"].Columns != null && ds.Tables["tblDeneme"].Rows != null)

Also you may use a control like this

Zbidi
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