css - HTML fixed header in table dynamically in ASP.NET -

i created table dynamically, being populated database. want created fixed header , scrollable body. tried css , javascript didn't manage anything, think because table created automatically. help.

here code:

    private void generatetable();     {         datatable dt = createdatatable();//in createdatatable take reocrds database         table table = new table();         tablerow row = null;          row = new tablerow();          (int j = 0; j < dt.columns.count; j++)         {             tableheadercell headercell = new tableheadercell();             headercell.text = dt.columns[j].columnname;             row.cells.add(headercell);         }         table.rows.add(row);          //add column values         (int = 0; < dt.rows.count; i++)         {             row = new tablerow();             (int j = 0; j < dt.columns.count; j++)             {                     tablecell cell = new tablecell();                     cell.text = dt.rows[i][j].tostring();                     row.cells.add(cell);             }             table.rows.add(row);          }         tablediv.controls.add(table);     } 

div add table:

   <div class="mainentry" style="width:90%" id="tablediv" runat="server" /> 

and css table:

table { border-collapse: collapse; width: 100%; color: white; }  th, td { text-align: left; padding: 8px; }  th{ font-size:20px; } tbody{ height:500px; overflow:auto; display:block; } tr:nth-child(even){background-color: rgba(255, 255, 255, .15)}  th { background-color: rgba(174, 183, 212, .15); color: white; } 

i hope css classes demo can you. visit fiddlehttp://jsfiddle.net/twenm/