protected override Expression VisitConstant(ConstantExpression node)
{
if (node.Value == null)
{
Out("null");
}
else
{
LinqParameterContainer container = node.Value as LinqParameterContainer;
if (container != null)
{
string stringValue = container.Property as string;
if (stringValue != null)
{
Out("\"" + stringValue + "\"");
}
else
{
Out(container.Property.ToString());
}
}
else
{
Out(node.Value.ToString());
}
}
return(node);
}
public void Parameterize_ProducesPropertyAccessOnConstant(object value)
{
Expression expr = LinqParameterContainer.Parameterize(value.GetType(), value);
LinqParameterContainer parameterizedValue = ((expr as MemberExpression).Expression as ConstantExpression).Value as LinqParameterContainer;
Assert.Equal(value, parameterizedValue.Property);
}
public static Expression Parameterize(Type type, object value)
{
// () => new LinqParameterContainer(constant).Property
// instead of returning a constant expression node, wrap that constant in a class the way compiler
// does a closure, so that EF can parameterize the constant (resulting in better performance due to expression translation caching).
LinqParameterContainer containedValue = LinqParameterContainer.Create(type, value);
return(Expression.Property(Expression.Constant(containedValue), "TypedProperty"));
}
