Generate DropDown values in EditForm of Library at runtime

If we want to generate values in one dropdown field dynamically in the EditForm.aspx of Library comparing to some value in other list.

Here in the following example we create a list having Username & Department columns.

Also create a library having the SubDepartment field as dropdown field which should show values according to the department of the current user in UsersDepartment list.


 <script runat="server">
protected void Page_Load(Object sender, EventArgs e)
{
   SPSecurity.RunWithElevatedPrivileges(delegate()
   {
      // Elevated Permission Code Goes Here
      using (SPSite spSite = SPContext.Current.Site)
      {
        using (SPWeb web = spSite.OpenWeb())
        {
           //Read List & Library
           SPList DepartmentList = web.Lists["UsersDepartment"];

           SPList MyDocumentList = web.Lists["MyDocumentLibrary"];
           //Read SubDepartment field from Library
           SPFieldChoice choicefield = (SPFieldChoice)MyDocumentList.Fields["SubDepartment"];
           SPQuery query = new SPQuery();
           //Get Current User  
               SPUser currentuser =SPContext.Current.Web.CurrentUser;
               string strcurrentuser = currentuser.LoginName.ToString();
               char[] arrSplit={'\\'};
               query.Query = @"<Where><Eq><FieldRef Name='User_x0020_Name'  /><Value Type='Text'>" + strcurrentuser.Split(arrSplit)[1] + @"</Value></Eq></Where>";           //Fetch listitems from DepartmentList
               SPListItemCollection collListItem = DepartmentList.GetItems(query);
                web.AllowUnsafeUpdates = true;
               if(collListItem.Count > 0)
               {
                 string department =collListItem[0]["Department"].ToString();
               if(department !="")              {
                if(department == "Science")
                {
                  choicefield.Choices.Clear();
                  choicefield.Choices.Add("Select Department");
                  choicefield.Choices.Add("Physics");
                  choicefield.Choices.Add("Chemistry");
                  choicefield.Choices.Add("Biology");
                  choicefield.Hidden=false;
                  choicefield.Required=true;
                  choicefield.Update();
                }
                else if(department == "Commerce")
                  choicefield.Choices.Clear();
                  choicefield.Choices.Add("Select Department");
                  choicefield.Choices.Add("Accounts");
                  choicefield.Choices.Add("Marketing");
                  choicefield.Hidden=false;
                  choicefield.Required=true;
                  choicefield.Update();
                }
              }
                else
                {
                   choicefield.Hidden=true;
                   choicefield.Required=false;
                   choicefield.Update();
                }
              }
              else
              {
                 choicefield.Hidden=true;
                 choicefield.Required=false;
                 choicefield.Update();
        }
          MyDocumentList.Update();
          web.AllowUnsafeUpdates = false;
      }
    }
  });
 }
  </script>





In the above code if the department of the current user is "Science" the values populated in the dropdown will be "Physics", "Chemistry" & "Biology".

This code runs at server side.

Copy the above code on the page where the above document library is rendered using SharePoint Designer.