I am just getting started with expression trees so I hope this makes sense. I am trying to create an expression tree to represent:
t => t.SomeProperty.Contains("stringValue");
So far I have got:
private static Expression.Lambda<Func<string, bool>> GetContainsExpression<T>(string propertyName, string propertyValue)
{
var parameterExp = Expression.Parameter(typeof(T), "type");
var propertyExp = Expression.Property(parameter, propertyName);
var containsMethodExp = Expression.*SomeMemberReferenceFunction*("Contains", propertyExp) //this is where I got lost, obviously :)
...
return Expression.Lambda<Func<string, bool>>(containsMethodExp, parameterExp); //then something like this
}
I just don't know how to reference the String.Contains() method.
Help appreciated.
Something like:
class Foo
{
public string Bar { get; set; }
}
static void Main()
{
var lambda = GetExpression<Foo>("Bar", "abc");
Foo foo = new Foo { Bar = "aabca" };
bool test = lambda.Compile()(foo);
}
static Expression<Func<T, bool>> GetExpression<T>(string propertyName, string propertyValue)
{
var parameterExp = Expression.Parameter(typeof(T), "type");
var propertyExp = Expression.Property(parameterExp, propertyName);
MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
var someValue = Expression.Constant(propertyValue, typeof(string));
var containsMethodExp = Expression.Call(propertyExp, method, someValue);
return Expression.Lambda<Func<T, bool>>(containsMethodExp, parameterExp);
}
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