CODEWITHSUNDEEP
c#sqloracle-database
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Reputation: 10464

OracleCommand ExecuteScalar sometimes returns null

I'm using the code below to do a scalar sql query in c#. Sometimes it fails with a NullReferenceException where I'm setting 'res'. Any ideas why this sometimes happens? (maybe when I do several queries at the same time) Note: I use the same query...and sometimes it returns null.

public void ExecScalarQuery(String query)
{
    OracleConnection conn = new OracleConnection(connectionString);
    try
    {
        conn.Open();
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = conn;
        cmd.CommandText = query;// "select count(*) from SALES_ADVENTUREWORKS2012.SALESORDERDETAIL where PRODUCTID=709";
        cmd.CommandType = CommandType.Text;
        cmd.CommandTimeout = QUERY_TIMEOUT;
        String res = cmd.ExecuteScalar().ToString();
    }
    finally
    {
        conn.Close();
    }
}

Upvotes: 1

Views: 7580

Answers (1)

DonBoitnott
DonBoitnott

Reputation: 11035

It is not unexpected that ExecuteScalar() might return a null value. Simply put, it happens because you ran a query that did not return a result set.

You should be taking care to catch that when it happens:

String res = "";
Object o = cmd.ExecuteScalar();
if (o != null)
    res = o.ToString();

Upvotes: 2

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