ConstraintEnumerator.cs

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using System.Collections;
 
namespace System.Data;
 
internal class ConstraintEnumerator
{
    private IEnumerator _tables;
 
    private IEnumerator _constraints;
 
    private Constraint _currentObject;
 
    protected Constraint CurrentObject => _currentObject;
 
    public ConstraintEnumerator(DataSet dataSet)
    {
        _tables = dataSet?.Tables.GetEnumerator();
        _currentObject = null;
    }
 
    public bool GetNext()
    {
        _currentObject = null;
        while (_tables != null)
        {
            if (_constraints == null)
            {
                if (!_tables.MoveNext())
                {
                    _tables = null;
                    return false;
                }
                _constraints = ((DataTable)_tables.Current).Constraints.GetEnumerator();
            }
            if (!_constraints.MoveNext())
            {
                _constraints = null;
                continue;
            }
            Constraint constraint = (Constraint)_constraints.Current;
            if (!IsValidCandidate(constraint))
            {
                continue;
            }
            _currentObject = constraint;
            return true;
        }
        return false;
    }
 
    public Constraint GetConstraint()
    {
        return _currentObject;
    }
 
    protected virtual bool IsValidCandidate(Constraint constraint)
    {
        return true;
    }
}