Question

我有以下功能，可以在类上搜索基于字符串的属性以进行文本匹配，我想缓存＆＃39;属性＆＃39; Match（）中的变量，因此每次运行类对象列表时都不会刷新。

public bool Match<T>(T item, string searchTerm)
{
    //You should cache the results of properties here for max perf.
    IEnumerable<Func<T, string>> properties = GetPropertyFunctions<T>();
    bool match = properties.Select(prop => prop(item)).Any(value => value != null && value.ToLower().Contains(searchTerm.ToLower()));
    return match;
}

public IEnumerable<Func<T, string>> GetPropertyFunctions<T>()
{
    var stringProperties = GetStringPropertyFunctions<T>();
    var decimalProperties = GetDecimalPropertyFunctions<T>();
    return stringProperties.Concat(decimalProperties);
}

public IEnumerable<Func<T, string>> GetStringPropertyFunctions<T>()
{
    var propertyInfos = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.GetProperty | BindingFlags.SetProperty)
        .Where(p => p.PropertyType == typeof(string)).ToList();

    var properties = propertyInfos.Select(GetStringPropertyFunc<T>);
    return properties;
}

public Func<T, string> GetStringPropertyFunc<T>(PropertyInfo propInfo)
{
    ParameterExpression x = System.Linq.Expressions.Expression.Parameter(typeof(T), "x");
    Expression<Func<T, string>> expression = System.Linq.Expressions.Expression.Lambda<Func<T, string>>(System.Linq.Expressions.Expression.Property(x, propInfo), x);
    Func<T, string> propertyAccessor = expression.Compile();
    return propertyAccessor;
}


public IEnumerable<Func<T, string>> GetDecimalPropertyFunctions<T>()
{
    var propertyInfos = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.GetProperty | BindingFlags.SetProperty)
        .Where(p => p.PropertyType == typeof(decimal)).ToList();

    var properties = propertyInfos.Select(GetDecimalPropertyFunc<T>);
    return properties;
}

public Func<T, string> GetDecimalPropertyFunc<T>(PropertyInfo propInfo)
{
    ParameterExpression x = System.Linq.Expressions.Expression.Parameter(typeof(T), "x");
    Expression<Func<T, decimal>> expression = System.Linq.Expressions.Expression.Lambda<Func<T, decimal>>(System.Linq.Expressions.Expression.Property(x, propInfo), x);
    Func<T, decimal> propertyAccessor = expression.Compile();
    return (T item) => propertyAccessor(item).ToString();
}

Answer 1

public static class FullTextSearch<T>
{
    private List<Func<T, string>> _properties;

    static FullTextSearch()
    {
        _properties = GetPropertyFunctions<T>().ToList();
    }

    public bool Match(T item, string searchTerm)
    {
        bool match = _properties.Select(prop => prop(item)).Any(value => value != null && value.ToLower().Contains(searchTerm.ToLower()));
        return match;
    }
}

Answer 2

将属性设为私有字段，并在首次使用时使用Lazy Wrapper对其进行初始化。你必须让其他方法静态才能像这样使用它，但这应该很容易实现。

private Lazy<IEnumerable<Func<T, string>>> properties = new Lazy<IEnumerable<Func<T, string>>>(GetPropertyFunctions<T>);

public bool Match<T>(T item, string searchTerm)
{
    bool match = properties.Value.Select(prop => prop(item)).Any(value => value != null && value.ToLower().Contains(searchTerm.ToLower()));
    return match;
}

如何缓存包含类属性的以下变量

2 个答案: