Delegating to properties in C#
I'm doing something with an Odbc DataReader. Each row in a query result should be transformed into a ResultObject
looking like this:
struct ResultObject {
public int Prop1 { get; set; }
public string Prop2 { get; set; }
...
}
In order to write mor开发者_运维百科e domain-specific code, I want to transform this code
var query = "SELECT Prop1, Prop2, ... FROM MyTable;";
... connect, submit query
while( reader.Read() ) {
var fieldValue = fields[ fieldindex ];
switch( fieldindex ) {
case( indexProp1 ): result.Prop1.Set( (int) fieldValue); break;
case( indexProp2 ): result.Prop2.Set( (string) fieldvalue); break;
...
}
}
into something more generic, where I build the mapping between indices and 'setters' dynamically:
But it would be nice to have something even more concise like:
PropMapper mappers[] = {
new PropMapper("Prop1", ResultType.Prop1 ),
new PropMapper("Prop2", ResultType.Prop2 ),
....
};
I have, however, no clue how to create a PropMapper
from the property of a ResultType
.
The question:
How can I generate an object that wraps/delegates to a property of a given type?
Note: though ORMs are quite useful for this, I'm really only asking how C# allows for creating the delegate (or anything equivalent)
PropMapper would need to receive a lambda expression as parameter, representing the property. Prism's NotificationObject receives such an expression on its RaisePropertyChanged event.
You can take a look on Prism's source code how the lambda expression is used to extract the property and use it.
You can try to use Reflection:
PropertyInfo[] props = new PropertyInfo[]
{
typeof(ResultObject).GetProperty("prop1"),
typeof(ResultObject).GetProperty("prop2"),
};
for (int i = 0; i < props.Length; i++)
{
props[i].SetValue(result, fieldValue, null);
}
You might want to take a look into a mini-orm like dapper
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