/// <summary>
/// 判定 exp 返回值肯定不是 null
/// </summary>
/// <param name="exp"></param>
/// <returns></returns>
public static bool AffirmExpressionRetValueIsNotNull(this DbExpression exp)
{
exp = DbExpressionExtension.StripConvert(exp);
if (exp.NodeType == DbExpressionType.Constant)
{
var c = (DbConstantExpression)exp;
return(c.Value != null && c.Value != DBNull.Value);
}
if (exp.NodeType == DbExpressionType.Parameter)
{
var p = (DbParameterExpression)exp;
return(p.Value != null && p.Value != DBNull.Value);
}
return(false);
}
/// <summary>
/// 判定 exp 返回值肯定是 null
/// </summary>
/// <param name="exp"></param>
/// <returns></returns>
public static bool AffirmExpressionRetValueIsNull(this DbExpression exp)
{
exp = DbExpressionExtension.StripConvert(exp);
if (exp.NodeType == DbExpressionType.Constant)
{
var c = (DbConstantExpression)exp;
return(c.Value == null || c.Value == DBNull.Value);
}
if (exp.NodeType == DbExpressionType.Parameter)
{
var p = (DbParameterExpression)exp;
return(p.Value == null || (p.Type == typeof(string) && string.IsNullOrEmpty(p.Value.ToString())) || p.Value == DBNull.Value);
}
return(false);
}