Best /Fastest way to read an Excel Sheet into a DataTable?

If you want to do the same thing in C# based on Ciarán Answer

string sSheetName = null;
string sConnection = null;
DataTable dtTablesList = default(DataTable);
OleDbCommand oleExcelCommand = default(OleDbCommand);
OleDbDataReader oleExcelReader = default(OleDbDataReader);
OleDbConnection oleExcelConnection = default(OleDbConnection);

sConnection = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Test.xls;Extended Properties=\"Excel 12.0;HDR=No;IMEX=1\"";

oleExcelConnection = new OleDbConnection(sConnection);
oleExcelConnection.Open();

dtTablesList = oleExcelConnection.GetSchema("Tables");

if (dtTablesList.Rows.Count > 0) 
{
    sSheetName = dtTablesList.Rows[0]["TABLE_NAME"].ToString();
}

dtTablesList.Clear();
dtTablesList.Dispose();


if (!string.IsNullOrEmpty(sSheetName)) {
    oleExcelCommand = oleExcelConnection.CreateCommand();
    oleExcelCommand.CommandText = "Select * From [" + sSheetName + "]";
    oleExcelCommand.CommandType = CommandType.Text;
    oleExcelReader = oleExcelCommand.ExecuteReader();
    nOutputRow = 0;

    while (oleExcelReader.Read())
    {
    }
    oleExcelReader.Close();
}
oleExcelConnection.Close();

here is another way read Excel into a DataTable without using OLEDB very quick Keep in mind that the file ext would have to be .CSV for this to work properly

private static DataTable GetDataTabletFromCSVFile(string csv_file_path)
{
    csvData = new DataTable(defaultTableName);
    try
    {
        using (TextFieldParser csvReader = new TextFieldParser(csv_file_path))
        {
            csvReader.SetDelimiters(new string[]
            {
                tableDelim 
            });
            csvReader.HasFieldsEnclosedInQuotes = true;
            string[] colFields = csvReader.ReadFields();
            foreach (string column in colFields)
            {
                DataColumn datecolumn = new DataColumn(column);
                datecolumn.AllowDBNull = true;
                csvData.Columns.Add(datecolumn);
            }

            while (!csvReader.EndOfData)
            {
                string[] fieldData = csvReader.ReadFields();
                //Making empty value as null
                for (int i = 0; i < fieldData.Length; i++)
                {
                    if (fieldData[i] == string.Empty)
                    {
                        fieldData[i] = string.Empty; //fieldData[i] = null
                    }
                    //Skip rows that have any csv header information or blank rows in them
                    if (fieldData[0].Contains("Disclaimer") || string.IsNullOrEmpty(fieldData[0]))
                    {
                        continue;
                    }
                }
                csvData.Rows.Add(fieldData);
            }
        }
    }
    catch (Exception ex)
    {
    }
    return csvData;
}

This seemed to work pretty well for me.

private DataTable ReadExcelFile(string sheetName, string path)
{

    using (OleDbConnection conn = new OleDbConnection())
    {
        DataTable dt = new DataTable();
        string Import_FileName = path;
        string fileExtension = Path.GetExtension(Import_FileName);
        if (fileExtension == ".xls")
            conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Import_FileName + ";" + "Extended Properties='Excel 8.0;HDR=YES;'";
        if (fileExtension == ".xlsx")
            conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + Import_FileName + ";" + "Extended Properties='Excel 12.0 Xml;HDR=YES;'";
        using (OleDbCommand comm = new OleDbCommand())
        {
            comm.CommandText = "Select * from [" + sheetName + "$]";
            comm.Connection = conn;
            using (OleDbDataAdapter da = new OleDbDataAdapter())
            {
                da.SelectCommand = comm;
                da.Fill(dt);
                return dt;
            }
        }
    }
}

public DataTable ImportExceltoDatatable(string filepath)
{
    // string sqlquery= "Select * From [SheetName$] Where YourCondition";
    string sqlquery = "Select * From [SheetName$] Where Id='ID_007'";
    DataSet ds = new DataSet();
    string constring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filepath + ";Extended Properties=\"Excel 12.0;HDR=YES;\"";
    OleDbConnection con = new OleDbConnection(constring + "");
    OleDbDataAdapter da = new OleDbDataAdapter(sqlquery, con);
    da.Fill(ds);
    DataTable dt = ds.Tables[0];
    return dt;
}

I have always used OLEDB for this, something like...

    Dim sSheetName As String
    Dim sConnection As String
    Dim dtTablesList As DataTable
    Dim oleExcelCommand As OleDbCommand
    Dim oleExcelReader As OleDbDataReader
    Dim oleExcelConnection As OleDbConnection

    sConnection = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Test.xls;Extended Properties=""Excel 12.0;HDR=No;IMEX=1"""

    oleExcelConnection = New OleDbConnection(sConnection)
    oleExcelConnection.Open()

    dtTablesList = oleExcelConnection.GetSchema("Tables")

    If dtTablesList.Rows.Count > 0 Then
        sSheetName = dtTablesList.Rows(0)("TABLE_NAME").ToString
    End If

    dtTablesList.Clear()
    dtTablesList.Dispose()

    If sSheetName <> "" Then

        oleExcelCommand = oleExcelConnection.CreateCommand()
        oleExcelCommand.CommandText = "Select * From [" & sSheetName & "]"
        oleExcelCommand.CommandType = CommandType.Text

        oleExcelReader = oleExcelCommand.ExecuteReader

        nOutputRow = 0

        While oleExcelReader.Read

        End While

        oleExcelReader.Close()

    End If

    oleExcelConnection.Close()

The ACE.OLEDB provider will read both .xls and .xlsx files and I have always found the speed quite good.