nullable decimal from SqlDataReader

Question

I use SqlDataReader to read some values from SQL data table. Value is decimal, but it call also be null. How do I assign it? I have tried it like this, but it throws "Specified cast is not valid" exception, if myValue is null.

decimal? d= (decimal)myRdr["myValue"];

What is the best way to do this?

Thank you.

possible duplicate of Finding null value in Dataset - DataRow.IsNull method vs ==DbNull.Value - c# — Nicholas Carey
– Nicholas Carey, Commented Feb 6, 2014 at 18:33
Not a duplicate of Finding null value in Dataset - DataRow.IsNull method vs ==DbNull.Value - c#, that is about testing if a value is null, this is about casting a nullable value from the reader to a variable — Andy Brown
– Andy Brown, Commented Feb 6, 2014 at 18:48

Selman Genç · Accepted Answer · 2014-02-06 18:17:52Z

3

How about this ?

decimal? d= myRdr["myValue"] == DBNull.Value ? null : (decimal?)myRdr["myValue"];

answered Feb 6, 2014 at 18:17

Selman Genç

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ekad · Accepted Answer · 2014-02-06 18:17:48Z

1

Try this:

decimal? d = myRdr["myValue"] != DBNull.Value ? (decimal)myRdr["myValue"] : null;

answered Feb 6, 2014 at 18:17

ekad

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dub stylee · Accepted Answer · 2014-02-06 18:19:27Z

1

This should work:

decimal? d = myRdr["myValue"] == DBNull.Value ? null : decimal.Parse(myRdr["myValue"].ToString());

answered Feb 6, 2014 at 18:19

dub stylee

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Andy Brown · Accepted Answer · 2014-02-06 18:51:29Z

0

decimal? d = myRdr[columnName] as decimal?;

And the above, in an extension method:

public static decimal? GetNullableDecimal(this SqlDataReader myRdr, string columnName, decimal? valueIfNull = null)
{
    return myRdr[columnName] as decimal? ?? valueIfNull;
}

Usage:

decimal? d = myRdr.GetNullableDecimal("myValue");
decimal? d = myRdr.GetNullableDecimal("myValue", valueIfNull: 0);

footnote

Disclaimer. I've only read this, not tested it: "as" casting is said to be 5x faster than prefix (explicit) casting: http://gen5.info/q/2008/06/13/prefix-casting-versus-as-casting-in-c/

edited Feb 6, 2014 at 18:51

answered Feb 6, 2014 at 18:19

Andy Brown

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