///// <summary>类型转换</summary>
///// <param name="obj"></param>
///// <returns></returns>
//public static implicit operator String(ConcatExpression obj)
//{
// return obj != null ? obj.GetString() : null;
//}
#endregion
#region 重载运算符
/// <summary>重载运算符实现And操作</summary>
/// <param name="exp"></param>
/// <param name="value">数值</param>
/// <returns></returns>
public static ConcatExpression operator &(WhereExpression exp, ConcatExpression value)
{
var left = exp.GetString();
var ce = new ConcatExpression(left);
if (value == null) return ce;
//return ce.And(value.GetString());
// 条件表达式遇上连接表达式，不需要And或者逗号，只需要一个空格
ce.Builder.Append(" ").Append(value.GetString());
return ce;
}
///// <summary>类型转换</summary>
///// <param name="obj"></param>
///// <returns></returns>
//public static implicit operator String(ConcatExpression obj)
//{
// return obj != null ? obj.GetString() : null;
//}
#endregion
#region 重载运算符
/// <summary>重载运算符实现And操作</summary>
/// <param name="exp"></param>
/// <param name="value">数值</param>
/// <returns></returns>
public static ConcatExpression operator &(WhereExpression exp, ConcatExpression value)
{
var left = exp.GetString();
var ce = new ConcatExpression(left);
if (value == null)
{
return(ce);
}
//return ce.And(value.GetString());
// 条件表达式遇上连接表达式，不需要And或者逗号，只需要一个空格
ce.Builder.Append(" ").Append(value.GetString());
return(ce);
}
///// <summary>按照指定若干个字段分组。没有条件时使用分组请用FieldItem的GroupBy</summary>
///// <param name="where"></param>
///// <param name="fields"></param>
///// <returns>返回条件语句加上分组语句</returns>
//public static ConcatExpression GroupBy(this WhereExpression where, params FieldItem[] fields)
//{
// var exp = new ConcatExpression();
// var sb = exp.Builder;
// where.GetString(sb, null);
// if (sb.Length > 0) sb.Append(" Group By ");
// for (var i = 0; i < fields.Length; i++)
// {
// if (i > 0) sb.Append(", ");
// sb.Append(fields[i].FormatedName);
// }
// return exp;
//}
/// <summary>按照指定若干个字段分组。没有条件时使用分组请用FieldItem的GroupBy</summary>
/// <param name="where"></param>
/// <param name="fields"></param>
/// <returns>将需要分组的字段作为ConcatExpression类型添加到whereExpression尾部</returns>
public static WhereExpression GroupBy(this WhereExpression where, params FieldItem[] fields)
{
var exp = new ConcatExpression();
for (var i = 0; i < fields.Length; i++)
{
if (i == 0)
{
exp &= fields[i].GroupBy();
}
exp.And(fields[i]);
}
return(new WhereExpression(where, Operator.Space, exp));
}
/// <summary>按照指定若干个字段分组。没有条件时使用分组请用FieldItem的GroupBy</summary>
/// <param name="fields"></param>
/// <returns>返回条件语句加上分组语句</returns>
public static ConcatExpression GroupBy(this WhereExpression where, params FieldItem[] fields)
{
var exp = new ConcatExpression();
var sb = exp.Builder;
where.GetString(sb, null);
if (sb.Length > 0)
{
sb.Append(" Group By ");
}
for (var i = 0; i < fields.Length; i++)
{
if (i > 0)
{
sb.Append(", ");
}
sb.Append(fields[i].FormatedName);
}
return(exp);
}