How do I set a field value in an C# Expression tree?

Question

Given:

FieldInfo field = ;
ParameterExpression targetExp = Expression.Parameter(typeof(T), \"target\");
ParameterExp         


        

Answer 1

I once made this class. Perhaps it helps:

public class GetterSetter
{
    private readonly Func getter;
    private readonly Action setter;
    private readonly string propertyName;
    private readonly Expression> propertyNameExpression;

    public EntityType Entity { get; set; }

    public GetterSetter(EntityType entity, Expression> property_NameExpression)
    {
        Entity = entity;
        propertyName = GetPropertyName(property_NameExpression);
        propertyNameExpression = property_NameExpression;
        //Create Getter
        getter = propertyNameExpression.Compile();
        // Create Setter()
        MethodInfo method = typeof (EntityType).GetProperty(propertyName).GetSetMethod();
        setter = (Action)
                 Delegate.CreateDelegate(typeof(Action), method);
    }


    public propType Value
    {
        get
        {
            return getter(Entity);
        }
        set
        {
            setter(Entity, value);
        }
    }

    protected string GetPropertyName(LambdaExpression _propertyNameExpression)
    {
        var lambda = _propertyNameExpression as LambdaExpression;
        MemberExpression memberExpression;
        if (lambda.Body is UnaryExpression)
        {
            var unaryExpression = lambda.Body as UnaryExpression;
            memberExpression = unaryExpression.Operand as MemberExpression;
        }
        else
        {
            memberExpression = lambda.Body as MemberExpression;
        }
        var propertyInfo = memberExpression.Member as PropertyInfo;
        return propertyInfo.Name;
    }

test:

var gs = new GetterSetter(new OnOffElement(), item => item.IsOn);
        gs.Value = true;
        var result = gs.Value;