Retrieve the value of a custom attribute's property's from a linq expression

I have the following attribute and a property decorated with that attribute:

[AttributeUsage(AttributeTargets.Property)]
public class TestAttribute : Attribute
{
    #region Properties
    public string Test { get; private set; }

    public string ResourceTest
    {
        get { return this.ResourceType.GetProperty(this.Test).GetValue(null) as string; }
    }

    public Type ResourceType { get; set; }
    #endregion

    #region Constructors
    public TestAttribute(string test)
    {
        this.Test = test;
    }
    #endregion
}

public class Test
{
    #region Properties
    [Test("TestRes", ResourceType = typeof(Resources.Test)]
    public string TestField { get; set; }
    #endregion
}

Now i need to retrieve the ResourceTest value from a Expression<Func<TModel, TValue>> but the following code gives me a TargetException at the returnline when i call GetResourceValue(o => o.TestField):

public static string GetResourceValue<TModel, TValue>(Expression<Func<TModel, TValue>> expression)
{
    MemberExpression memberExpression = expression.Body as MemberExpression;
    if (memberExpression != null && memberExpression.Member != null)
    {
        foreach (var attribute in memberExpression.Member.CustomAttributes)
        {
            switch (attribute.AttributeType.Name)
            {
                case "TestAttribute":
                    return (attribute.AttributeType.GetProperty("ResourceTest").GetValue(attribute) as string);
            }
        }
    }
    return null;
}

Is there another way to retrieve that property's value?