Q:

how can get all excel sheet name in c# using OleDbDataAdapter

               _conn = new OleDbConnection(_connectionStrting);
                _conn.Open();
                DataTable dt = _conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                String[] sheetNames = new String[dt.Rows.Count];
                int i = 0;

                foreach (DataRow row in dt.Rows)
                {
                    sheetNames[i] = row["TABLE_NAME"].ToString();
                    comboBox2.Items.Add(sheetNames[i]);
                    i++;
                }

                _conn.Close();

this code works for me but I want to know if have a solution with OleDbDataAdapter

A:

OleDbDataAdaptor has nothing to do with Sheet names; Sheet names belong to Excel.Workbook, and Excel Workbook belongs to Excel.Application.
You would need to iterate through workbook sheet names: 
using Excel = Microsoft.Office.Interop.Excel;

Excel.Application xl = new Excel.Application();;
Excel.Workbook wb = xl.Workbooks.Open("WorkBookfullPath", 0, true);

foreach (Excel.Worksheet ws in wb.Worksheets) {
        {
             string wsName = ws.Name;  
        }

You don't really need here OleDbDataAdapter, in this case (in case you need to read data from worksheet) you can just read from Excel into 2 dimentional array (1st dimension is rows and second dimension is columns):
object[,] data = ws.UsedRange.Value2; // change UsedRange range to your table range, and  you can also use ws.UsedRange.FormulaR1C1

