fetch dropdownlist selected value in NeedDatasource event of radgrid in asp.net ajax web application

I want to fetch value from dropdownlist when selected. On that selection of value I am firing a simple select query ie.

"select * from Catego开发者_C百科ry where cat_name ='" + dropdownlistselectedvalue + "'"

here is the code of needDatasource

protected void rdgridview_NeedDataSource(object sender, Telerik.Web.UI.GridNeedDataSourceEventArgs e) { if (!e.IsFromDetailTable) {

//I want to fetch the dropdownlist selected value here ie

          string dpvalue = DropDownList1.SelectedValue.ToString();

      string strqry = "select * from Categories where Category_Name = '"+ dpvalue +"'";

        rdgridview.DataSource = getDataTable(strqry);            
    }
}

But I am not able to fetch the value from the dropdownlist selected value in needDatasource method. How shall I fetch the value or fire any event of dropdownlist control?

Thanks in advance

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Telerik has a detailed documentation. You might want to try simple data binding. Check it here. For NeedsDataSource documentation, check here.

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You can do that easily by saving the dropdownlist selected value in a ViewState, do that in the SelectedIndexChanged event for the dropdownlist .

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    ViewState["List1_Value"] = DropDownList1.SelectedValue.ToString();

} 

then get the value from ViewState in the needDatasource event:

string strqry = "select * from Categories where Category_Name = '" + ViewState["List1_Value"]+ "'";