private readonly Dictionary <ExpressionNodeType, Func <ExpressionNode, Expression> > expressionAction; // Templates.
#region ctor
/// <summary>
/// Creates a new instance of <see cref="ExpressionBuilder{T, TResult}"/>.
/// </summary>
public ExpressionBuilder()
{
this.ItemType = typeof(T);
this.Properties = ItemType.GetCachedProperties();
this.ParameterExpression = Expression.Parameter(this.ItemType, "item");
expressionAction = new Dictionary <ExpressionNodeType, Func <ExpressionNode, Expression> >()
{
{ ExpressionNodeType.RelationalOperator, BuildRelationalExpression },
{ ExpressionNodeType.ArithmeticOperator, BuildArithmeticExpression },
{ ExpressionNodeType.LogicalOperator, BuildLogicalOperator },
{ ExpressionNodeType.PropertyType, BuildValueExpression },
{ ExpressionNodeType.StringType, BuildValueExpression },
{ ExpressionNodeType.DateType, BuildValueExpression },
{ ExpressionNodeType.UnknownType, BuildValueExpression }
};
}
/// <summary>
/// Converts from <see cref="ExpressionNode"/> to <see cref="Expression"/>
/// when the <see cref="ExpressionOperatorType"/> is a value expression.
/// </summary>
private Expression BuildValueExpression(ExpressionNode expression, ExpressionNodeType type)
{
Expression rdo;
string content;
PropertyInfo pi;
content = expression.FormattedText ?? expression.Text;
switch (type)
{
case ExpressionNodeType.StringType:
if (content.StartsWith("'") && content.EndsWith("'"))
{
content = content.Substring(1, content.Length - 2);
}
rdo = Expression.Constant(content);
break;
case ExpressionNodeType.DateType:
if (content.StartsWith("#") && content.EndsWith("#"))
{
content = content.Substring(1, content.Length - 2);
}
rdo = Expression.Constant(DateTime.Parse(content, CultureInfo.InvariantCulture));
break;
case ExpressionNodeType.PropertyType:
if (content.StartsWith("[") && content.EndsWith("]"))
{
content = content.Substring(1, content.Length - 2);
}
pi = ItemType.GetCachedProperties()[content];
rdo = Expression.Property(this.ParameterExpression, pi);
break;
case ExpressionNodeType.UnknownType:
Double dbl;
bool bln;
// Adivinar tipo. Probar número, boolean, propiedad... Al final, si no se identifica, dejar como object.
if (Double.TryParse(content, NumberStyles.Number, CultureInfo.InvariantCulture, out dbl))
{
rdo = Expression.Constant(dbl);
}
else if (Boolean.TryParse(content, out bln))
{
rdo = Expression.Constant(bln);
}
else if (Properties.TryGetValue(content, out pi))
{
rdo = BuildValueExpression(expression, ExpressionNodeType.PropertyType);
}
else
{
rdo = Expression.Constant(content, typeof(object)); // TODO: Mas averiguaciones.
}
break;
default:
throw new NotImplementedException(); // TODO: Tipo no permitido.
}
return(rdo);
}
