how do I filter data from gridview which binded by dataset

this is read property for dataset if dataset is null then return null otherwise return dataset value from viewstate

debug your code and check which line showing this error

Iam using dropdown list for the paging 

only write properties in gridview  AllowPaging="true" PageSize="10"

and on event OnPageIndexChanging

  grdSearch.PageIndex = e.NewPageIndex;
        fncBindGrid();// this is function where You write the code on page load to bind gridview

you can use paging in gridview by settiong allowpaging="true" and pagesize="10" pagesize depend on  you

sir before u only sended me link of asp sippest for paging the gridview so that worked.
but here for paging need IDataReader coz its coming from sql query if bind dataset then cant do paging.

sorry,i have never used Idatareader
You can try to check
otherwise use dataset

But here iam binding the gridview from "IDataReader" object for paging the gridview, so can I have to create IDataReader object globally instead of dataset? My gridview bind code is below.

yes but
DataSet dsAcc = new DataSet();
 you have created object here
instead you
 declare dataset globally  in viewstate as


public DataSet Ds
    {
        get
        {
            object temp = ViewState["Ds"];
            return temp == null ? null : temp as DataSet;
        }
        set
        {
            ViewState["Ds"] = value;
        }
    }

Oh,so can I write like below instead of "dataset = objdal.FillDataSet(CommandType.StoredProcedure, "sp_getTopic");"


 connection.Open();
                command = new SqlCommand();
                command.CommandText = "sp_Get_CustInfoSerach";
                command.CommandType = CommandType.StoredProcedure;
                command.Connection = connection;
                command.Parameters.AddWithValue("@PageIndex", pageIndex);
                command.Parameters.AddWithValue("@PageSize", int.Parse(ddlPaging.SelectedValue));
                command.Parameters.Add("@RecordCount", SqlDbType.Int, 4);
                command.Parameters["@RecordCount"].Direction = ParameterDirection.Output;
                SqlParameter outParam = command.Parameters.Add("@bal", SqlDbType.Float);
                outParam.Direction = ParameterDirection.Output;
                SqlDataAdapter daAcc = new SqlDataAdapter(command);
                DataSet dsAcc = new DataSet();


                daAcc.Fill(dsAcc);

I have write
  Ds = objdal.FillDataSet(CommandType.StoredProcedure, "sp_getTopic");
for a example to show to bind dataset
you have to write your query/procedure to bind dataset

I was using DAL class and methods to fill dataset from database and bind dataset to gridview
 

yes

   if (!Page.IsPostBack)
            {

//code to bind
}

step 1 initialize dataset globaaly above page load in viewstate
as

  public DataSet Ds
    {
        get
        {
            object temp = ViewState["Ds"];
            return temp == null ? null : temp as DataSet;
        }
        set
        {
            ViewState["Ds"] = value;
        }
    }

step 2

bind gridview on postback check

  Ds = objdal.FillDataSet(CommandType.StoredProcedure, "sp_getTopic");
        if (Ds.Tables[0].Rows.Count > 0)
        {         
                 
                    grdSearch.DataSource = Ds.Tables[0];
                    grdSearch.DataBind();                  
                }             

               
            }

step 3

on search buttonclick


 string strFieldNm;
            strFieldNm = ddl_Search.Text.Trim();
            if (strFieldNm == "Category")
            {
                strFieldNm = "category_name";
            }
            if (strFieldNm == "Class")
            {
                strFieldNm = "class_name";
            }
          
            if (txt_Search.Text.Trim().Length > 0)
            {
                DataTable dt = new DataTable();
                dt = Ds.Tables[0];
                 dt.DefaultView.RowFilter = "Convert([" + strFieldNm + "],'System.String')  Like '" + txt_Search.Text.Trim().Replace("'", "''") + "%'  ";
                grdSearch.DataSource = dt;
                 grdSearch.DataBind();

}

here i have search by dropdown(by columnname of database you want to search) and textbox for keyword you want to search


i have bind dropdown statically as
Category,Class  and  category_name,class_name are columnname from dataset

I hope It may help you