Invalid data has been used to update the list item. The field you are trying to update may be read only | The property or field has not been initialized. It has not been requested or the request has not been executed. It may need to be explicitly requested

Issue1: Invalid data has been used to update the list item. The field you are trying to update may be read only.

Issue2: The property or field has not been initialized. It has not been requested or the request has not been executed. It may need to be explicitly requested.

Problem Code:

internal static Void GetFileFromTempDocLib(ClientContext clientContext1)  

{

                var folderRelativeUrl = "";

                Web web = clientContext.Web;                

                clientContext.Load(web, w1 => w1.ServerRelativeUrl, w1 => w1.Url);

                clientContext.ExecuteQuery();

                folderRelativeUrl = web.ServerRelativeUrl;

}

Solution Code:

internal static Void GetFileFromTempDocLib(ClientContext clientContext1)  

{

                var folderRelativeUrl = "";

                Web web = clientContext.Web;

                try

                {

                    folderRelativeUrl = web.ServerRelativeUrl;

                }

                catch (PropertyOrFieldNotInitializedException ex)

                {

                    clientContext.Load(web, w1 => w1.ServerRelativeUrl, w1 => w1.Url);

                    clientContext.ExecuteQuery();

                    folderRelativeUrl = web.ServerRelativeUrl;

                }

}