I have a requirement to quickly load a DataTable into an Excel sheet, where cells should automatically format to correspond to the DataTable’s column types. This is particularly important for DateTime columns.
This works fine, cells with DateTime values becomes formatted as “Date” in Excel.
But, if the value being imported is null (or System.DBNull actually, since DataTable uses this to represent null values), the cell remains formatted as “General”.
Here’s what I tried:
- A custom ICellsDataTable interface (to explictly return null for DBNull values)
- NumberFormats collection, to explicitly specify the number format for the DateTime column to “YYYY-MM-DD”.
But nothing works. I know I can write code that iterates over the cells that should be formatted as Date, but that is too slow and clunky.
Is there any other way to get empty data (DateTime) to become formatted as “Date” when importing data using Aspose?
Using Aspose.Cells for .NET, 25.10.0
Here’s the code:
using System.Data;
using System.Diagnostics;
using Aspose.Cells;
using DateTimeFormat;
class Program
{
static void Main()
{
// Create a sample DataTable
var table = new DataTable("MyTable");
table.Columns.Add("ColInt", typeof(int));
table.Columns.Add("ColString", typeof(string));
table.Columns.Add("ColDateTime", typeof(DateTime));
table.Rows.Add(1, "Hello", DateTime.UtcNow.Date.AddHours(9));
table.Rows.Add(2, "World", DateTime.UtcNow.Date.AddHours(10));
table.Rows.Add(3, null, null);
// Create a new Workbook and import the DataTable
var wb = new Workbook();
var ws = wb.Worksheets[0];
var opts = new ImportTableOptions
{
IsFieldNameShown = true,
NumberFormats = new string[] { null, null, "YYYY-MM-DD" },
ConvertNumericData = false,
};
ws.Cells.ImportData(table, 0, 0, opts);
ws.Cells.ImportData(new CellsDataTable(table), 10, 0, opts);
ws.AutoFitColumns();
// Save with unique name
var fileName = $"ImportData_{DateTime.Now:yyyyMMdd_HHmmss}.xlsx";
var fullPath = Path.Combine(Directory.GetCurrentDirectory(), fileName);
wb.Save(fullPath);
Console.WriteLine($"Saved: {fullPath}");
// Try to open the file in Excel
try
{
Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
Console.WriteLine("Opening in Excel (if installed)...");
}
catch (Exception ex)
{
Console.WriteLine($"Could not open automatically: {ex.Message}");
}
}
}
And the ICellsDataTable implementation:
using Aspose.Cells;
using System.Data;
namespace DateTimeFormat
{
internal class CellsDataTable : ICellsDataTable
{
private readonly DataTable tbl;
private int currentRowIndex = -1;
public CellsDataTable(DataTable tbl)
{
this.tbl = tbl;
}
public object this[int columnIndex]
{
get
{
object dbValue = tbl.Rows[currentRowIndex][columnIndex];
if (dbValue.GetType() == typeof(DBNull) && tbl.Columns[columnIndex].DataType == typeof(System.DateTime))
{
return null;
}
else
{
return dbValue;
}
}
}
public object this[string columnName]
{
get
{
return tbl.Rows[currentRowIndex][columnName];
}
}
public string[] Columns => tbl.Columns.Cast<DataColumn>().Select(c => c.ColumnName).ToArray();
public int Count => tbl.Rows.Count;
public void BeforeFirst() => currentRowIndex = -1;
public bool Next() => ++currentRowIndex < tbl.Rows.Count;
}
}
