Insert a value from a dropdown to a lookup column in SharePoint Online using CSOM/C#

Question

I have a dropdown with values from a column named Title(Single line of text)

The end goal is to store these values from the dropdown to a lookup column named Team.

Read a few articles here , However did not find a resolution to my issue.

C# Code

private void AddEmployee()
        {
            try
            {
                string login = "******";
                string password = "******";
                SecureString securepassword = new SecureString();

                foreach (char c in password)

                { securepassword.AppendChar(c); }

                ClientContext ctx = new ClientContext("https://site.sharepoint.com/sites/test");
                ctx.Credentials = new SharePointOnlineCredentials(login, securepassword);
                Web site = ctx.Web;
                List list = site.Lists.GetByTitle("Employee");
                CamlQuery query = CamlQuery.CreateAllItemsQuery();
                var items = list.GetItems(query);
                ctx.Load(items);
                ctx.ExecuteQuery();

                foreach (var oListItem in items)
                 {    

                    oListItem["Title"] = txtName.Text.ToString();
                    oListItem["Age"] = txtAge.Text;
                    oListItem["Address"] = txtAddress.Text;
                    FieldLookupValue lookup = oListItem["Team"] as FieldLookupValue;
                lookup.LookupId = team.SelectedIndex;
                oListItem["Team"] = lookup;
                    oListItem.Update();
                    
                }

                ScriptManager.RegisterStartupScript(this, this.GetType(), "script", "alert('Data Inserted Successfully...');", true);
            }
            catch (ApplicationException ex)
            {
                Page.ClientScript.RegisterStartupScript(this.GetType(), "ErrorAlert", "Error Occured" + ex.Message, true);
            }
        }

The code runs without any errors , However no data is saved to the respective columns.

Would appreciate if anyone could assist me.

Update

Modified the code as below , However no values are saved

FieldLookupValue lookup = oListItem["Team"] as FieldLookupValue;
lookup.LookupId = team.SelectedIndex;
oListItem["Team"] = lookup;

Also wrote the ctx.ExecuteQuery(); before ScriptManager.RegisterStartupScript(this, this.GetType(), "script", "alert('Data Inserted Successfully...');", true); and got the error

The collection has not been initialized. It has not been requested or the request has not been executed. It may need to be explicitly requested.

Answer 1

I think you are missing ctx.ExecuteQuery(); after updating items.

Try adding ctx.ExecuteQuery(); before this line:

ScriptManager.RegisterStartupScript(this, this.GetType(), "script", "alert('Data Inserted Successfully...');", true);

Answer 2

Kindly use the below code snippet for setting the look-up field value:

foreach (var oListItem in items)
{    
    oListItem["Title"] = txtName.Text.ToString();
    oListItem["Age"] = txtAge.Text;
    oListItem["Address"] = txtAddress.Text;
    
    FieldLookupValue lookup = oListItem["Team"] as FieldLookupValue;
    lookup.LookupId = lID; // assign the selected value of the drop-down Team
    oListItem["Team"] = lookup;
    oListItem.Update();
}

---

Edit:

private void AddEmployee()
{
    try
    {
        string login = "******";
        string password = "******";
        SecureString securepassword = new SecureString();

        foreach (char c in password)
        { securepassword.AppendChar(c); }

        ClientContext ctx = new ClientContext("https://site.sharepoint.com/sites/test");
        ctx.Credentials = new SharePointOnlineCredentials(login, securepassword);
        Web site = ctx.Web;
        List list = site.Lists.GetByTitle("Employee");
        
        ListItemCreationInformation listCreationInformation = new ListItemCreationInformation();  
        ListItem oListItem = list.AddItem(listCreationInformation);  
        
        oListItem["Title"] = txtName.Text.ToString();
        oListItem["Age"] = txtAge.Text;
        oListItem["Address"] = txtAddress.Text;
        FieldLookupValue lookup = oListItem["Team"] as FieldLookupValue;
        lookup.LookupId = team.SelectedIndex;
        oListItem["Team"] = lookup;
        oListItem.Update();  
        ctx.ExecuteQuery();  
        
        ScriptManager.RegisterStartupScript(this, this.GetType(), "script", "alert('Data Inserted Successfully...');", true);
    }
    catch (ApplicationException ex)
    {
            Page.ClientScript.RegisterStartupScript(this.GetType(), "ErrorAlert", "Error Occured" + ex.Message, true);
    }
}