Casewhere.Runtime.IO Namespace

var reader = Readers.GetExcelReader();
using(reader.Open(documentApi.OpenRead(ctx.Input.DocumentAttribute)))
{
    var workSheetReader = reader.GetSheet(0);
    var rowCount = workSheetReader.RowCount;
    var columnCount = workSheetReader.ColumnCount;
    for (int row = 0; row < rowCount; row++) {
        for (int col = 0; col < columnCount; col++) {
            var value = workSheetReader.Read<string>(row, col);
        }
    }
}

var filter = FilterBuilder.Create().Build();
var schools = dataApi.Search(DataObjectApiQuery.For("School").FilterBy(filter)).Data;
using(var stream = new MemoryStream())
{
    using (var writer = Writers.GetExcelWriter())
    {
        writer.Open(stream);
        var sheetWriter = writer.AddSheet("Sheet1");
        var row = 0;
        foreach(dynamic school in schools) {            
            sheetWriter.Write(row, 0, school.Name);
            sheetWriter.Write(row, 1, school.Description);
            row ++;
        }       
    }   

    // Note: MUST move the cursor to the beginning of the stream before storing.
    stream.Seek(0, SeekOrigin.Begin);
    var documentInfo = documentApi.Create("Sample.xlsx");
    documentApi.Store(documentInfo, stream);
}