'DynamicFlatTreeDataGridSource<Person, int>' does not contain a definition for 'GetColumnStates' and no accessible extension method 'GetColumnStates' accepting a first argument of type 'DynamicFlatTreeDataGridSource<Person, int>' could be found (are you missing a using directive or an assembly reference?)

'DynamicFlatTreeDataGridSource<Person, int>' does not contain a definition for 'GetColumnStates' and no accessible extension method 'GetColumnStates' accepting a first argument of type 'DynamicFlatTreeDataGridSource<Person, int>' could be found (are you missing a using directive or an assembly reference?)

Process completed with exit code 1.

The member 'DynamicFlatTreeDataGridSource<TModel, TModelKey>.Dispose()' does not hide an accessible member. The new keyword is not required.

Non-nullable property 'ColumnStates' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Non-nullable field '_source' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

The member 'DynamicFlatTreeDataGridSource<TModel, TModelKey>.Dispose()' does not hide an accessible member. The new keyword is not required.

Non-nullable property 'ColumnStates' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Dereference of a possibly null reference.

Dereference of a possibly null reference.