is that possible to automate these mappings with reflection?
i have a simple column mapping :
var columnsMap = new Dictionary<string, Expression<Func<Industry, object>>>
{
["id"] = v => v.Id,
["name"] = v => v.Name,
["isActive"] = v => v.IsActive
};
columnsMap run-time result:
i want to automate these mappings in a wrapper class:
public class QueryColumnMapper<T> : Dictionary<string, Expression<Func<T, object>>>
{
public QueryColumnMapper<T> GenerateMappings()
{
foreach (var item in typeof(T).GetProperties())
{
// get dictionary key ======> its OK
var name = Char.ToLowerInvariant(item.Name[0]) + item.Name.Substring(1); //camel-case name
// get expression =======> this is the problem. wrong way
Expression<Func<T, object>> exp = v => v.GetType().GetProperty(item.Name);
//Expression<Func<T, object>> exp = v => v.?????; <-----
// add to mapper object
this.Add(name, exp);
}
return this;
}
}
example of using this class:
var columnsMap = new QueryColumnMapper<Industry>().GenerateMappings();
i don't know is that possible to get my expression dynamically in run-time?
( i'm using this mapping dictionary for apply filtering on entity-framework IQueryable
query. with first example (manual mapping) its working but i don't know how to do that in run-time without manual mapping )
You can build a custom expression manually using the property name
// x =>
var parameter = Expression.Parameter(typeof(T));
// x.Name
var mapProperty = Expression.Property(parameter, "Name");
// (object)x.Name
var convertedExpression = Expression.Convert(mapProperty, typeof(object));
// x => (object)x.Name
var exp = Expression.Lambda<Func<T, object>>(convertedExpression, parameter);
If this is a common subset and you find you're doing it quite often you can create a base interface.
for other viewers i shared final code :
public class QueryColumnMapper<T>
{
public QueryColumnMapper()
{
Mappings = new Dictionary<string, Expression<Func<T, object>>>();
}
public Dictionary<string, Expression<Func<T, object>>> Mappings { get; set; }
public Dictionary<string, Expression<Func<T, object>>> GenerateMappings()
{
foreach (var item in typeof(T).GetProperties())
{
var name = Char.ToLowerInvariant(item.Name[0]) + item.Name.Substring(1); //camel-case name
// add to mapper object
Mappings.Add(name, GetExpression(item.Name));
}
return Mappings;
}
private Expression<Func<T,object>> GetExpression(string propertyName)
{
// x =>
var parameter = Expression.Parameter(typeof(T));
// x.Name
var mapProperty = Expression.Property(parameter, propertyName);
// (object)x.Name
var convertedExpression = Expression.Convert(mapProperty, typeof(object));
// x => (object)x.Name
return Expression.Lambda<Func<T, object>>(convertedExpression, parameter);
}
}
usage:
var columnsMap = new QueryColumnMapper<Industry>().GenerateMappings();