protected virtual ColumnAssignment VisitColumnAssignment(ColumnAssignment ca)
{
ColumnExpression c = (ColumnExpression)this.Visit(ca.Column);
Expression e = this.Visit(ca.Expression);
return(this.UpdateColumnAssignment(ca, c, e));
}
protected ColumnAssignment UpdateColumnAssignment(ColumnAssignment ca, ColumnExpression c, Expression e)
{
if (c != ca.Column || e != ca.Expression)
{
return(new ColumnAssignment(c, e));
}
return(ca);
}
protected override ColumnAssignment VisitColumnAssignment(ColumnAssignment ca)
{
ca = base.VisitColumnAssignment(ca);
Expression expression = ca.Expression;
NamedValueExpression nv = null;
if (expression.NodeType == ExpressionType.Constant)
{
var value = (expression as ConstantExpression).Value;
if (value == null)
{
TypeAndValue tv = new TypeAndValue(ca.Column.Type, null);
if (!this.map.TryGetValue(tv, out nv))
{
string name = "p" + (iParam++);
nv = new NamedValueExpression(name, SqlType.Get(ca.Column.Type), Expression.Constant(null, ca.Column.Type));
this.map.Add(tv, nv);
}
expression = nv;
}
else
{
var columnType = ca.Column.Type;
if (columnType.IsNullable())
{
columnType = Nullable.GetUnderlyingType(columnType);
}
if (columnType != value.GetType())
{
value = Converter.Convert(value, columnType);
expression = Expression.Constant(value);
}
}
}
nv = expression as NamedValueExpression;
if (nv != null)
{
expression = new NamedValueExpression(nv.Name, ca.Column.SqlType, nv.Value);
}
return(this.UpdateColumnAssignment(ca, ca.Column, expression));
}
protected virtual ReadOnlyCollection <ColumnAssignment> VisitColumnAssignments(ReadOnlyCollection <ColumnAssignment> assignments)
{
List <ColumnAssignment> alternate = null;
for (int i = 0, n = assignments.Count; i < n; i++)
{
ColumnAssignment assignment = this.VisitColumnAssignment(assignments[i]);
if (alternate == null && assignment != assignments[i])
{
alternate = assignments.Take(i).ToList();
}
if (alternate != null)
{
alternate.Add(assignment);
}
}
if (alternate != null)
{
return(alternate.AsReadOnly());
}
return(assignments);
}
