Reading Excel files from C#

Is there a free or open source library to read Excel files (.xls) directly from a C# program?

It does not need to be too fancy, just to select a worksheet and read the data as strings. So far, I've been using Export to Unicode text function of Excel, and parsing the resulting (tab-delimited) file, but I'd like to eliminate the manual step.

var fileName = string.Format("{0}\\fileNameHere", Directory.GetCurrentDirectory());
var connectionString = string.Format("Provider=Microsoft.Jet.OLEDB.4.0; data source={0}; Extended Properties=Excel 8.0;", fileName);

var adapter = new OleDbDataAdapter("SELECT * FROM [workSheetNameHere$]", connectionString);
var ds = new DataSet();

adapter.Fill(ds, "anyNameHere");

DataTable data = ds.Tables["anyNameHere"];

This is what I usually use. It is a little different because I usually stick a AsEnumerable() at the edit of the tables:

var data = ds.Tables["anyNameHere"].AsEnumerable();

as this lets me use LINQ to search and build structs from the fields.

var query = data.Where(x => x.Field<string>("phoneNumber") != string.Empty).Select(x =>
                new MyContact
                    {
                        firstName= x.Field<string>("First Name"),
                        lastName = x.Field<string>("Last Name"),
                        phoneNumber =x.Field<string>("Phone Number"),
                    });

If it is just simple data contained in the Excel file you can read the data via ADO.NET. See the connection strings listed here:

http://www.connectionstrings.com/?carrier=excel2007 or http://www.connectionstrings.com/?carrier=excel

-Ryan

Update: then you can just read the worksheet via something like select * from [Sheet1$]

The ADO.NET approach is quick and easy, but it has a few quirks which you should be aware of, especially regarding how DataTypes are handled.

This excellent article will help you avoid some common pitfalls: http://blog.lab49.com/archives/196

This is what I used for Excel 2003:

Dictionary<string, string> props = new Dictionary<string, string>();
props["Provider"] = "Microsoft.Jet.OLEDB.4.0";
props["Data Source"] = repFile;
props["Extended Properties"] = "Excel 8.0";

StringBuilder sb = new StringBuilder();
foreach (KeyValuePair<string, string> prop in props)
{
    sb.Append(prop.Key);
    sb.Append('=');
    sb.Append(prop.Value);
    sb.Append(';');
}
string properties = sb.ToString();

using (OleDbConnection conn = new OleDbConnection(properties))
{
    conn.Open();
    DataSet ds = new DataSet();
    string columns = String.Join(",", columnNames.ToArray());
    using (OleDbDataAdapter da = new OleDbDataAdapter(
        "SELECT " + columns + " FROM [" + worksheet + "$]", conn))
    {
        DataTable dt = new DataTable(tableName);
        da.Fill(dt);
        ds.Tables.Add(dt);
    }
}