Extension method return using generics

Question

Is it possible to return a generic type using extension methods?

For example, I have the following method:

// Convenience method to obtain a field within a row (as a double type) 
public static double GetDouble(this DataRow row, string field) {
    if (row != null && row.Table.Columns.Contains(field))
    {
        object value = row[field];
        if (value != null && value != DBNull.Value)
            return Convert.ToDouble(value);
    }
    return 0;
}

This is currently used as follows:

double value = row.GetDouble("tangible-equity");

but I would like to use the following code:

double value = row.Get<double>("tangible-equity");

Is this possible and if so, what would the method look like?

Answer 1

How about this one:

    public static T Get<T>(this DataRow row, string field) where T: IConvertible 
    {
        if (row != null && row.Table.Columns.Contains(field))
        {
            object value = row[field];
            if (value != null && value != DBNull.Value)
                return (T)Convert.ChangeType(value, typeof(T));
        }
        return default(T);
    }

Convert.ChangeType is much more flexible handling conversions as opposed to just casting. This pretty much reflects your original code, just generic.