c# - Edit two Columns in GridView keeping other Columns' data intact -

i have grideview in asp.net project , want edit 2 columns , used read-only="true" property problem after editing 2 columns data of others become empty !!!! please me how avoid problem.

<columns>    <asp:hyperlinkfield datanavigateurlfields="rnum" datanavigateurlformatstring="webform2.aspx?rnum={0}" datatextfield="rnum" headertext="no" />    <asp:boundfield datafield="title" headertext="title" sortexpression="title" readonly="true"/>    <asp:boundfield datafield="assignto" headertext="assignto" sortexpression="assignto" />    <asp:boundfield datafield="priority"   headertext="priority" sortexpression="priority" readonly="true" />    <asp:boundfield datafield="status" headertext="status" sortexpression="status" />    <asp:boundfield datafield="username"   headertext="requested by" sortexpression="username" readonly="true" />    <asp:boundfield datafield="ddate"  headertext="date" sortexpression="ddate" readonly="true" /> </columns> 

you have modify underlying sqldatasource update command property, in following example:

updatecommand="update employees set firstname=@firstname,lastname=@lastname,title=@title employeeid=@employeeid" 

(re: https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.sqldatasource.updatecommand(v=vs.110).aspx)