private DataSet LoadExcel(string fileName, string tableName)
{
string path = fileName;
string connStr = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=Excel 12.0;";
System.Data.OleDb.OleDbConnection MyConnection;
System.Data.DataSet DtSet;
System.Data.OleDb.OleDbDataAdapter MyCommand;
MyConnection = new System.Data.OleDb.OleDbConnection(connStr);
MyConnection.Open();
DataTable dtExcelSchema;
dtExcelSchema = MyConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables, null);
string SheetName = dtExcelSchema.Rows[0]["TABLE_NAME"].ToString();
MyCommand = new System.Data.OleDb.OleDbDataAdapter("select * from [" + SheetName + "]", MyConnection);
MyCommand.TableMappings.Add("Table", tableName);
DtSet = new System.Data.DataSet();
MyCommand.Fill(DtSet);
MyConnection.Close();
return DtSet;
}

Workbook book = '.....xyz''';
if (book.HasPassword) { ... }

try
    {
        MyConnection.Open();
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }