//Checks to see if a related unique constraint exists
//if it doesn't then a unique constraint is created.
//if a unique constraint can't be created an exception will be thrown
private void _ensureUniqueConstraintExists(ConstraintCollection collection,
DataColumn [] parentColumns)
{
//not null
if (null == parentColumns)
{
throw new ArgumentNullException(
"ParentColumns can't be null");
}
UniqueConstraint uc = null;
//see if unique constraint already exists
//if not create unique constraint
if (parentColumns[0] != null)
{
uc = UniqueConstraint.GetUniqueConstraintForColumnSet(parentColumns[0].Table.Constraints, parentColumns);
}
if (null == uc)
{
uc = new UniqueConstraint(parentColumns, false); //could throw
parentColumns [0].Table.Constraints.Add(uc);
}
//keep reference
_parentUniqueConstraint = uc;
_parentUniqueConstraint.ChildConstraint = this;
}
internal override void AddToConstraintCollectionSetup(
ConstraintCollection collection)
{
for (int i = 0; i < Columns.Length; i++)
{
if (Columns[i].Table != collection.Table)
{
throw new ArgumentException("These columns don't point to this table.");
}
}
//run Ctor rules again
_validateColumns(_dataColumns);
//make sure a unique constraint doesn't already exists for these columns
UniqueConstraint uc = UniqueConstraint.GetUniqueConstraintForColumnSet(collection, this.Columns);
if (null != uc)
{
throw new ArgumentException("Unique constraint already exists for these" +
" columns. Existing ConstraintName is " + uc.ConstraintName);
}
//Allow only one primary key
if (this.IsPrimaryKey)
{
uc = GetPrimaryKeyConstraint(collection);
if (null != uc)
{
uc._isPrimaryKey = false;
}
}
// if constraint is based on one column only
// this column becomes unique
if (_dataColumns.Length == 1)
{
_dataColumns[0].SetUnique();
}
if (IsConstraintViolated())
{
throw new ArgumentException("These columns don't currently have unique values.");
}
_belongsToCollection = true;
}