Invalid attempt to read when no data is present.

[Helixpoint]

Dim dr1 As SqlDataReader = MachCodeListID.GetSingleMachCode(thecodesID)

' Read first row from database

dr1.Read()

If IsDBNull(dr1("CATNUM")) Then '**************** This is where I am getting
the error??????

thecatnum = 0

Else

thecatnum = dr1("CATNUM")

End If


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[Marina]

Looks like there were no rows returned. dr1.Read returned false.

 

[Helixpoint]

Not to be a jerk, but I figured that out.

Looks like there were no rows returned. dr1.Read returned false.

 

[Marina]

If you figured out that no rows were returned, then what's the problem?

 

[Helixpoint]

I get an error when it checks for NULL???

If you figured out that no rows were returned, then what's the problem?

 

[Marina]

If there was no row returned, there is now way to check if a column in that
row is null - because there is no row in the first place!!!

 

[Marina]

There is no point to doing that. dr1.Read returned false - hence no rows.
Neither of these things will work. The structure needs to be

If dr1.Read() Then

If IsDbNull(dr1("Catnum") Then
.....
End If

End If

 

[daphish]

oops my bad you could do it as
dr1("catnum") is nothing

 

[Marina]

No, my point is you could not do anything that would mean getting the column
value from the datareader.

The mere call to dr1("catnum") raises the error. There is no row - so no
column value for "catnum" - because there is no row!!

That's why the if statement for dr1.Read - to make sure there is a row
before you try to look at one of its columns.