Merge pull request #97 from alustrement-bob/fix-string-null-value

Fix set null value on string property

Author: acupofjose

Postgrest/Table.cs

@@ -474,13 +474,13 @@ public IPostgrestTable<TModel> Set(Expression<Func<TModel, object>> keySelector,
                 throw new ArgumentException(
                     "Expression should return a KeyValuePair with a key of a Model Property and a value.");
 
-            if (value == null)
+            if (value == null && visitor.ExpectedType != typeof(string))
             {
                 if (Nullable.GetUnderlyingType(visitor.ExpectedType) == null)
                     throw new ArgumentException(
                         $"Expected Value to be of Type: {visitor.ExpectedType.Name}, instead received: {null}.");
             }
-            else if (!visitor.ExpectedType.IsInstanceOfType(value))
+            else if (value != null && !visitor.ExpectedType.IsInstanceOfType(value))
             {
                 throw new ArgumentException(string.Format("Expected Value to be of Type: {0}, instead received: {1}.",
                     visitor.ExpectedType.Name, value.GetType().Name));

PostgrestTests/LinqTests.cs

@@ -129,6 +129,10 @@ await client.Table<KitchenSink>()
             await client.Table<KitchenSink>()
                 .Set(x => x.BooleanValue, true)
                 .Update();
+
+            await client.Table<KitchenSink>()
+                .Set(x => x.StringValue!, null)
+                .Update();
         }
 
         [TestMethod("Linq: OnConflict")]