Hi mahesh213,

Use string Replace method. Refer below code.

C#

[HttpPost]
public JsonResult PopulateTable(Detail values)
{
    TestEntities db = new TestEntities();
    // Getting the query from Report1 table.
    string query = db.Report1.Where(x => x.RId == values.RId).Select(x => x.Rquery).FirstOrDefault();
    // Check values if not null then control present and replace value.
    if (values.details != null)
    {
        for (int i = 0; i < values.details.Count; i++)
        {
            string key = "{" + values.details[i].Text + "}";
            string value = "'" + values.details[i].Value + "'";
            // Replace the place holder with value.
            query = query.Replace(key, value);
        }
    }
    query = query.Replace("####", Session["Id"].ToString());
    // Execute your final query and return json result and bind the gridview on success function.
    // Your code to return json.
    return Json(null, JsonRequestBehavior.AllowGet);
}