/// <summary>
/// 生成一个查询项
/// </summary>
/// <param name="field">相关的属性（字段）</param>
/// <param name="paramName">参数名，仅作为记录</param>
/// <param name="oprater">操作方法</param>
internal QueryParamProviderItem(Expression <Func <T, TKey> > field, Expression <Func <TKey, bool> > when, string paramName, QueryParamProviderOprater oprater)
{
Field = field;
When = when;
ParamName = paramName;
Oprater = oprater;
}
/// <summary>
/// 添加一个参数查询项
/// </summary>
/// <typeparam name="TKey">参数字段类型</typeparam>
/// <param name="field">参数字段 请统一表达式参数名</param>
/// <param name="oprater">比较符号 默认为相等</param>
/// <param name="when">参数生效条件 默认为不为默认值(string 的默认值为 不为null和string.Empty)</param>
/// <param name="paramName">参数在键值对里的名称 默认为和字段名称一致</param>
public void AddItem <TKey>(Expression <Func <T, TKey> > field, QueryParamProviderOprater oprater = QueryParamProviderOprater.Equal, Expression <Func <TKey, bool> > when = null, string paramName = null)
{
if (paramName == null)
{
paramName = ((MemberExpression)field.Body).Member.Name;
}
if (when == null)
{
var vvv = default(TKey);
ParameterExpression para = Expression.Parameter(typeof(TKey));
when = Expression.Lambda <Func <TKey, bool> >(Expression.NotEqual(para, Expression.Constant(vvv)), para) as Expression <Func <TKey, bool> >;
//////////////////////////////////对string 的默认值进行处理
if (typeof(TKey) == typeof(string))
{
when = when.And(Expression.Lambda <Func <TKey, bool> >(Expression.NotEqual(para, Expression.Constant(string.Empty)), para));
}
}
QueryParamProviderItem <T, TKey> item = new QueryParamProviderItem <T, TKey>(field, when, paramName, oprater);
Items.Add(item);
}
