throw null exception when parse int arrays with only 1item in ExcelQueryClass

[lazism]

Hello. I have been using ExcelParse temporarily since the api v3 version deprecated.

I found that ExcelQuery class throws null exception when there is only one item in the int array.

ExcelQuery.cs -> Line 272 - 288

    /// <summary>
    /// Convert type of cell value to its predefined type which is specified in the sheet's ScriptMachine setting file.
    /// </summary>
    protected object ConvertFrom(ICell cell, Type t)
    {
        object value = null;

        if (t == typeof(float) || t == typeof(double) || t == typeof(short) || t == typeof(int) || t == typeof(long))
        {
            if (cell.CellType == NPOI.SS.UserModel.CellType.Numeric)
            {
                value = cell.NumericCellValue;
            }
            else if (cell.CellType == NPOI.SS.UserModel.CellType.String)
            {
                //Get correct numeric value even the cell is string type but defined with a numeric type in a data class.
                if (t == typeof(float))
                    value = Convert.ToSingle(cell.StringCellValue);
                if (t == typeof(double))
                    value = Convert.ToDouble(cell.StringCellValue);
                if (t == typeof(short))
                    value = Convert.ToInt16(cell.StringCellValue);
                if (t == typeof(int))
                    value = Convert.ToInt32(cell.StringCellValue);
                if (t == typeof(long))
                    value = Convert.ToInt64(cell.StringCellValue);
            }
            else if (cell.CellType == NPOI.SS.UserModel.CellType.Formula)
            {
                // Get value even if cell is a formula
                if (t == typeof(float))
                    value = Convert.ToSingle(cell.NumericCellValue);
                if (t == typeof(double))
                    value = Convert.ToDouble(cell.NumericCellValue);
                if (t == typeof(short))
                    value = Convert.ToInt16(cell.NumericCellValue);
                if (t == typeof(int))
                    value = Convert.ToInt32(cell.NumericCellValue);
                if (t == typeof(long))
                    value = Convert.ToInt64(cell.NumericCellValue);
            }
        }
        else if (t == typeof(string) || t.IsArray)
        {
            // HACK: handles the case that a cell contains numeric value
            //       but a member field in a data class is defined as string type.
            //       e.g. string s = "123"
            if (cell.CellType == NPOI.SS.UserModel.CellType.Numeric)
                value = cell.NumericCellValue;
            else
                value = cell.StringCellValue;
        }
        else if (t == typeof(bool))
            value = cell.BooleanCellValue;

        if (t.IsGenericType && t.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
        {
            var nc = new NullableConverter(t);
            return nc.ConvertFrom(value);
        }

        if (t.IsEnum)
        {
            // for enum type, first get value by string then convert it to enum.
            value = cell.StringCellValue;
            return Enum.Parse(t, value.ToString(), true);
        }
        else if (t.IsArray)
        {
            if (t.GetElementType() == typeof(float))
                return ConvertExt.ToSingleArray((string)value);

            if (t.GetElementType() == typeof(double))
                return ConvertExt.ToDoubleArray((string)value);

            if (t.GetElementType() == typeof(short))
                return ConvertExt.ToInt16Array((string)value);

            if (t.GetElementType() == typeof(int))
                return ConvertExt.ToInt32Array((string)value);

            if (t.GetElementType() == typeof(long))
                return ConvertExt.ToInt64Array((string)value);

            if (t.GetElementType() == typeof(string))
                return ConvertExt.ToStringArray((string)value);
        }

        // for all other types, convert its corresponding type.
        return Convert.ChangeType(value, t);
    }
}

Forced (string)value conversion is not allowed in the code if there is only one item.
I temporarily modified the code to value.ToString() and now the code has not thrown NullException.

[Kim, Hyoun Woo]

Thank you for reporting.
Would you make a pull request for this? So, let me clearly know what is going on and even apply the changes easily.

Cheers,