How to loops over a dataset's table's DataRowCollection without null checking

Question

I'm working with a dataset that is already populated. I am iterating over the rows in a table like so:

foreach (DataRow row in this.dataSet.Tables["tablename"].Rows)
{
    // do something
}

this works fine, unless there are no rows, in which case there is no table, so I get an 'object not set to an instance of an object' style error. (i.e. this.dataSet.Tables["tablename"] is null so I'm in effect calling null.Rows, which of course borks).

To get around this I'm doing:

if (this.dataSet.Tables.Contains("tablename"))
{
    foreach (DataRow row in this.dataSet.Tables["tablename"].Rows)
    {
        // do something
    }
}

which is, frankly, ugly as sin. I'm guessing this is because .net returns null not a null object.

Is there a way that I can simply loop over a table's rows, that if the table doesn't exist loops over an empty collection?

Answer 1

No you can't. Best thing you can do is hide the checking in an extension method.

If table exist, return the table rows, otherwise return empty sequence.

public static class DataSetExtensions
{
    public static IEnumerable<DataRow> RowsOfTable(this DataSet dataSet, string tableName)
    {
        if (dataSet.Tables.Contains(tableName))
            return dataSet.Tables[tableName].AsEnumerable();
        return Enumerable.Empty<DataRow>();
    }
}

Then use it as

DataSet dataSet = new DataSet();
foreach (DataRow row in dataSet.RowsOfTable("tablename"))
{
    // do something
}