Dapper sql in

應用場景：

使用 sql的 Case When Then 批量更新某張表，底層數據庫用到了Dapper

代碼示例：

public int UpdateClientReceivedResult(Dictionary<string, string> dict)
        {
            var dynamicSqlParam = new DynamicParameters();
            var sbSet = new StringBuilder(256);
            sbSet.Append(" (CASE SmsFlowID ");
            int idx = 0;
            foreach (var kv in dict)
            {
                sbSet.Append(string.Format(" WHEN @SmsFlowID{0} THEN @ClientReceivedResult{0} ", idx));
                dynamicSqlParam.Add(string.Format("SmsFlowID{0}", idx), kv.Key, null, null, null);
                dynamicSqlParam.Add(string.Format("ClientReceivedResult{0}", idx), kv.Value, null, null, null);
                idx += 1;
            }
            sbSet.Append(" ELSE ClientReceivedResult END) ");

            var sbWhere = new StringBuilder(256);
            sbWhere.Append(" AND SmsFlowID in @ids ");
            dynamicSqlParam.Add("ids", dict.Keys.ToArray(), null, null, null);

            string sql = string.Format("UPDATE [SmsSendResult] SET  [ClientReceivedResult]={0} WHERE 1=1 {1}", sbSet,
                sbWhere);
            int affectNum = -1;
            using (var conn = new SqlConnection(SmsDBConnString))
            {
                affectNum = conn.Execute(sql, dynamicSqlParam);
            }
            return affectNum;
        }

最終生成的sql：

UPDATE [SmsSendResult] SET  [ClientReceivedResult]= (CASE SmsFlowID  WHEN @SmsFlowID0 THEN @ClientReceivedResult0  WHEN @SmsFlowID1 THEN @ClientReceivedResult1  WHEN @SmsFlowID2 THEN @ClientReceivedResult2  WHEN @SmsFlowID3 THEN @ClientReceivedResult3  WHEN @SmsFlowID4 THEN @ClientReceivedResult4  WHEN @SmsFlowID5 THEN @ClientReceivedResult5  WHEN @SmsFlowID6 THEN @ClientReceivedResult6  WHEN @SmsFlowID7 THEN @ClientReceivedResult7  ELSE ClientReceivedResult END)  WHERE 1=1  AND SmsFlowID in @SmsFlowID

代碼說明：
這個方法的作用是，根據傳進來的Dict<SmsFlowID,ClientReceivedResult>批量更新SmsSendResult對應的值，為了限定更新的條數，需要用到where in操作，in后面的參數名必須要注意一下，盡量不和別的參數名字有重復，我之前sbWhere是這么寫的：

var sbWhere = new StringBuilder(256);
sbWhere.Append(" AND SmsFlowID in @SmsFlowID ");
dynamicSqlParam.Add("SmsFlowID", dict.Keys.ToArray(), null, null, null);

結果運行報異常：說什么已存在相同參數名SmsFlowID1。。。找了半天，原來是in的參數名字的問題！Dapper對於 where col in @arg 會將動態參數的數組類型的參數自動轉化為 where col in (@arg1,@arg2....)，這樣就重名了，所以找了半天原因，原來是這么個回事，修改后程序運行正常