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#](http://stackoverflow.com/questions/5599390/finding-null-value-in-dataset-datarow-isnull-method-vs-dbnull-value-c-shar) — Nicholas Carey, Feb 06 '14 at 18:33
Not a duplicate of [Finding null value in Dataset - DataRow.IsNull method vs ==DbNull.Value - c#](http://stackoverflow.com/questions/5599390/finding-null-value-in-dataset-datarow-isnull-method-vs-dbnull-value-c-shar), that is about testing if a value is null, this is about casting a nullable value from the reader to a variable — Andy Brown, Feb 06 '14 at 18:48

score 3 · Accepted Answer · answered Feb 06 '14 at 18:17

3

How about this ?

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

answered Feb 06 '14 at 18:17

Selman Genç

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score 1 · Answer 2 · answered Feb 06 '14 at 18:17

1

Try this:

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

answered Feb 06 '14 at 18:17

ekad

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score 1 · Answer 3 · answered Feb 06 '14 at 18:19

1

This should work:

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

answered Feb 06 '14 at 18:19

dub stylee

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Andy Brown · Answer 4 · 2014-02-06T18:51:29.807

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/

nullable decimal from SqlDataReader

4 Answers4