C＃我如何獲得主鍵的最大值

Question

我的問題是如何獲得表中的主鍵的最大值，將其增加1，然後將該結果放入特定的文本框中。稍後插入文本以數據庫作爲新紀錄。謝謝

Answer 1

這可能會導致程序運行緩慢，如果數據庫包含噸的記錄，但它適用於我。

DataTable myDataTable = new DataTable(); 
/* 
Add record from primary key column to datatable 
*/ 

//Add primary key from datatable to List<int> 
List<int> primaryKeyList = new List<int>(); 
foreach (DataRow row in myDataTable.Rows) 
{ 
    primaryKeyList.Add(Int32.Parse(row[0].ToString())); 
} 

int maxKey = primaryKeyList.Max(); 
primaryKeyList.Clear(); 
myDataTable.Dispose(); 
/* 
Do whatever you want with maxKey 
*/ 

或

DataTable myDataTable = new DataTable(); 
/* 
Add record from primary key column to datatable 
*/ 

int maxKey = 0; 
//Find max key 
foreach (DataRow row in myDataTable.Rows) 
{ 
    if(Int32.Parse(row[0].ToString()) > maxKey) maxKey = Int32.Parse(row[0].ToString()); 
} 

myDataTable.Dispose(); 
/* 
Do whatever you want with maxKey 
*/