How to query and display excel data by using ASP.NET, ADO.NET, and Visual C# .NET

found this article very helpful
http://support.microsoft.com/kb/306572/

I modified it a bit to work for me (I am using RadUpload to get the file):

// Create connection string variable. Modify the "Data Source"
// parameter as appropriate for your environment.
String sConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;" +
"Data Source=" + ruImporter.UploadedFiles[0].FileName+";" +
"Extended Properties=Excel 8.0;";

// Create connection object by using the preceding connection string.
OleDbConnection objConn = new OleDbConnection(sConnectionString);

// Open connection with the database.
objConn.Open();

// The code to follow uses a SQL SELECT command to display the data from the worksheet.

// Create new OleDbCommand to return data from worksheet.
OleDbCommand objCmdSelect = new OleDbCommand("SELECT * FROM [Sheet1$]", objConn);


// Create new OleDbDataAdapter that is used to build a DataSet
// based on the preceding SQL SELECT statement.
OleDbDataAdapter objAdapter1 = new OleDbDataAdapter();

// Pass the Select command to the adapter.
objAdapter1.SelectCommand = objCmdSelect;

// Create new DataSet to hold information from the worksheet.
DataSet objDataset1 = new DataSet();

// Fill the DataSet with the information from the worksheet.
objAdapter1.Fill(objDataset1);



// Clean up objects.
objConn.Close();