static class QueryableExtensions
{
private static MethodInfo StringContainsMethod;
private static MethodInfo StringStartsWithMethod;
static QueryableExtensions()
{
Type[] singleStringParam = new[] { typeof(string) };
StringContainsMethod = typeof(string).GetMethod("Contains", singleStringParam);
StringStartsWithMethod = typeof(string).GetMethod("StartsWith", singleStringParam);
}
public static IQueryable<T> AppendTextFilter<T>(this IQueryable<T> queryable, Expression<Func<T, string>> memberSelector, string condition, string value)
{
Expression expression = null;
switch (condition)
{
case "StartsWith":
expression = Expression.Call(memberSelector.Body, StringStartsWithMethod, Expression.Constant(value));
break;
case "Equals":
expression = Expression.Equal(memberSelector.Body, Expression.Constant(value));
break;
case "Contains":
expression = Expression.Call(memberSelector.Body, StringContainsMethod, Expression.Constant(value));
break;
default:
throw new NotSupportedException(string.Format("'{0}' is not a supported condition", condition));
}
var lambda = Expression.Lambda<Func<T, bool>>(expression, memberSelector.Parameters);
return queryable.Where(lambda);
}
}
当我在谷歌上搜索时,我得到了上面的类。嗯,它真的帮了我很多,但它仍然不能满足我的需要。
问题是它只能处理“字符串”类型的字段。正如您在上面的代码块中看到的,该方法只能处理 T,string 。
我如何在一个方法中处理我想要的任何类型?