插入重复记录LINQ

Question

我试图插入使用下面的LINQ查询。不知何故，我得到了ID的重复记录。有人能帮我解释细节吗？

try { 
OLA_ASSESSMENT_DTL OAD = db.OLA_ASSESSMENT_DTL.SingleOrDefault(
    ev => ev.OAD_RIV_ID == id); 

transaction = "Modify"; // resetting the value of the variable 
if (OAD == null) { 
    transaction = "Add"; 
    OAD = new OLA_ASSESSMENT_DTL(); 
} 
OAD.OAD_PER_RELAIONSHIP = relationshipfocus.relationshipfocus; 
OAD.OAD_PER_RELAIONSHIP_COMMENT = CRecHelper.CheckIsNullString(relationshipfocus.strrelationshipfocus).ToString(); 
OAD.OAD_RIV_ID = id;  
OAD.OAD_MODIFIED_DATE = DateTime.Now; 
if (transaction == "Add") { 
    db.OLA_ASSESSMENT_DTL.Add(OAD); 
} 
db.SaveChanges(); 
} 

Answer 1

起初，你正确地检测重复记录（虽然你可能应该使用FirstOrDefault代替SingleOrDefault，但是这是一个细节）：

OLA_ASSESSMENT_DTL OAD = db.OLA_ASSESSMENT_DTL.SingleOrDefault(
     ev => ev.OAD_RIV_ID == id); 

transaction = "Modify"; // resetting the value of the variable 
if (OAD == null) 
{ 
    transaction = "Add"; 
    OAD = new OLA_ASSESSMENT_DTL(); 
} 

但后来，你随便的ID分配给对象即使你知道这是一个重复：

OAD.OAD_RIV_ID = id; 

首先，删除了这一行，因为它是无用的：

• 如果记录已经存在，那么你只是覆盖ID与当前值
• 如果记录是重复的，那么你设置的新的记录重复的ID

相反，设置一个唯一的ID，当你知道的记录是重复的，下面您为表定义为准策略：

OLA_ASSESSMENT_DTL OAD = db.OLA_ASSESSMENT_DTL.SingleOrDefault(
     ev => ev.OAD_RIV_ID == id); 

transaction = "Modify"; // resetting the value of the variable 
if (OAD == null) 
{ 
    transaction = "Add"; 
    OAD = new OLA_ASSESSMENT_DTL(); 
    // TODO: Assign a unique id, or let the database assign one if the column is auto-increment 
}