Moves read/write locking and isolation level to the responsibility of the sql provider based on the db type

src/Umbraco.Core/Persistence/SqlSyntax/SqlCeSyntaxProvider.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
+using System.Data.SqlServerCe;
 using System.Linq;
 using NPoco;
 using Umbraco.Core.Persistence.DatabaseAnnotations;
@@ -52,6 +54,8 @@ namespace Umbraco.Core.Persistence.SqlSyntax
             return "(" + string.Join("+", args) + ")";
         }
 
+        public override System.Data.IsolationLevel DefaultIsolationLevel => System.Data.IsolationLevel.RepeatableRead;
+
         public override string FormatColumnRename(string tableName, string oldName, string newName)
         {
             //NOTE Sql CE doesn't support renaming a column, so a new column needs to be created, then copy data and finally remove old column
@@ -152,6 +156,39 @@ where table_name=@0 and column_name=@1", tableName, columnName).FirstOrDefault()
             return result > 0;
         }
 
+        public override void WriteLock(IDatabase db, params int[] lockIds)
+        {
+            // soon as we get Database, a transaction is started
+
+            if (db.Transaction.IsolationLevel < IsolationLevel.RepeatableRead)
+                throw new InvalidOperationException("A transaction with minimum RepeatableRead isolation level is required.");
+
+            db.Execute(@"SET LOCK_TIMEOUT 1800;");
+            // *not* using a unique 'WHERE IN' query here because the *order* of lockIds is important to avoid deadlocks
+            foreach (var lockId in lockIds)
+            {
+                var i = db.Execute(@"UPDATE umbracoLock SET value = value*-1 WHERE id=@id", new { id = lockId });
+                if (i == 0) // ensure we are actually locking!
+                    throw new Exception($"LockObject with id={lockId} does not exist.");
+            }
+        }
+        
+        public override void ReadLock(IDatabase db, params int[] lockIds)
+        {
+            // soon as we get Database, a transaction is started
+
+            if (db.Transaction.IsolationLevel < IsolationLevel.RepeatableRead)
+                throw new InvalidOperationException("A transaction with minimum RepeatableRead isolation level is required.");
+
+            // *not* using a unique 'WHERE IN' query here because the *order* of lockIds is important to avoid deadlocks
+            foreach (var lockId in lockIds)
+            {
+                var i = db.ExecuteScalar<int?>("SELECT value FROM umbracoLock WHERE id=@id", new { id = lockId });
+                if (i == null) // ensure we are actually locking!
+                    throw new Exception($"LockObject with id={lockId} does not exist.");
+            }
+        }
+
         protected override string FormatIdentity(ColumnDefinition column)
         {
             return column.IsIdentity ? GetIdentityString(column) : string.Empty;