How to make column Editable in Gridview

Question

Hi

  In below code i want SessionDate to be editable in all rows

SQLUtility sQLUtility = new SQLUtility();
DataTable dt = sQLUtility.GeBookPlanningRecommendation(HRpl, BookCollection, StudentCollection).Tables[0];
if (dt != null)
{
    DataColumn Remarks = new DataColumn("Remarks", typeof(string));
    dt.Columns.Add(Remarks);
    DataColumn Dates = new DataColumn("SessionDate", typeof(string));
    dt.Columns.Add(Dates);

    grdPlanning.DataSource = dt;
    grdPlanning.DataBind();
}

Thanks