public QueryablePipeline From(string variable, Expression source)
{
var elementType = GetElementType(source.Type);
var result = new QueryablePipeline
{
Variable = variable,
QueryableExpr = source,
Parameter = Expression.Parameter(elementType, variable)
};
// TODO: Unversal search for extension method container
if (typeof(IQueryable <>).MakeGenericType(elementType).IsAssignableFrom(source.Type))
{
result.MethodContainerType = typeof(Queryable);
}
else if (typeof(IEnumerable <>).MakeGenericType(elementType).IsAssignableFrom(source.Type))
{
result.MethodContainerType = typeof(Enumerable);
}
else
{
throw new InvalidOperationException(
"Unable to find extension method container for type '" + source.Type.FullName + "'");
}
scope[variable] = result.Parameter;
return(result);
}
public Expression FromSelect(QueryablePipeline pipeline, Expression expression)
{
var inElementType = pipeline.ElementType;
var outElementType = expression.Type;
var selectorDelegateType = typeof(Func <,>).MakeGenericType(inElementType, outElementType);
var selectorExpr = Expression.Lambda(
selectorDelegateType,
expression,
pipeline.Parameter);
return
(Expression.Call(
pipeline.MethodContainerType,
"Select",
new Type[]
{
inElementType,
outElementType
},
pipeline.QueryableExpr,
selectorExpr));
}
public QueryablePipeline Where(QueryablePipeline pipeline, Expression condExpr)
{
var predicateType = typeof(Func <,>).MakeGenericType(pipeline.ElementType, typeof(bool));
var predicate = Expression.Lambda(
predicateType,
condExpr,
pipeline.Parameter);
return(new QueryablePipeline
{
QueryableExpr =
Expression.Call(
pipeline.MethodContainerType,
"Where",
new Type[] { pipeline.ElementType },
pipeline.QueryableExpr,
predicate),
Variable = pipeline.Variable,
Parameter = pipeline.Parameter,
MethodContainerType = pipeline.MethodContainerType
});
}
