CODEWITHSUNDEEP
c#lambdaexpression-trees
Kelmen
Kelmen

Reputation: 1063

How to pass a lambda expression to a method expecting lambda expression?

I have an extension method to get a property name as string:

    public static string GetPropertyName<T, TResult>(this T obj, Expression<Func<T, TResult>> propertyId)
    {
        return ((MemberExpression)propertyId.Body).Member.Name;
    }

Now I have another method, expecting to pass in list (param) of this kind of property lamba expression. I want this new method to reuse the 1st method, but can't figure out how to pass it over

    public string Test<T>(params Expression<Func<T, object>>[] ps)
    {
        foreach (var p in ps)
        {
                var howToCodeThis = p.GetPropertyName(dummy => dummy);

expected usage:

                var result = Test<Something>(request.Sorting
                , x => x.prop1
                , x => x.prop2
                , x => x.prop3
                );

Update: Backs answer worked once I change my GetPropertyName to cater for UnaryExpression:

    public static string GetPropertyName<T, TResult>(this T obj, Expression<Func<T, TResult>> propertyId)
    {
        if (propertyId.Body is MemberExpression)
            return ((MemberExpression)propertyId.Body).Member.Name;

        if (propertyId.Body is UnaryExpression)
        {
            var op = ((UnaryExpression)propertyId.Body).Operand;
            return ((MemberExpression)op).Member.Name;
        }

        throw new NotImplementedException(string.Format("GetPropertyName - {0}", propertyId.Body.GetType().FullName));
    }

Upvotes: 2

Views: 219

Answers (1)

Backs
Backs

Reputation: 24903

var howToCodeThis = GetPropertyName(default(T), p);

OR

var howToCodeThis = default(T).GetPropertyName(p);

But I noteced, you don't use obj in GetPropertyName method.

Upvotes: 1

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