What is returned if a select statement returns no rows?

I'm working with SQL now in my programming, and I'm q开发者_StackOverflow中文版uerying a database, like so.

scCommand = new SqlCommand("SELECT LegislationID FROM Legislation WHERE Number =  @ECERegulation", sconConnection);
        scCommand.Parameters.Add("@ECERegulation", SqlDbType.NVarChar);
        scCommand.Parameters["@ECERegulation"].Value = strECERegulation;

        return (int)scCommand.ExecuteScalar();

My question is, what would be returned if my parameter did not match anything in the table that I am querying? I need to have an if statement to deal with a non-matching ECERegulation. Would it return null? Or would it return the LegislationID of zero? Any help would be appreciated.

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The docs:

Return Value
The first column of the first row in the result set, or a null reference (Nothing in Visual Basic) if the result set is empty. Returns a maximum of 2033 characters.

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If no record is found, it would return NULL. So you would get a casting error.

You need to check the result for nullity before casting. And also decided whether to throw an exception or return zero, depending on your business rules.

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You can match the null by using Nullable< int >. You can also pass the casting error and return null like this.

int? GetSomething()
{
     .....
     .....
     return (int?)TypeDescriptor.GetConverter(typeof(int?)).ConvertFrom(scCommand.ExecuteScalar());
}