C＃我如何获得主键的最大值

Question

我的问题是如何获得表中的主键的最大值，将其增加1，然后将该结果放入特定的文本框中。稍后插入文本以数据库作为新纪录。谢谢

Answer 1

这可能会导致程序运行缓慢，如果数据库包含吨的记录，但它适用于我。

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 
*/