使用C#向SQL Server插入数据时，报错Object reference not set to an instance of an object

Question

代码如下：
连续插入很多条数据，其中就会突然报两次Object reference not set to an instance of an object.

DbConnection cnn;(这里是提前new过的，一直保持的连接状态)
string sqlString = "INSERT INTO [dbo].[Events] VALUES (N'{XXXXXXXX-XXXX-XXXX-XXXXXXXXXXXXXX}',1000,N"HAHA');
DbCommand cmd = new SqlCommand(queryString,cnn as SqlConnction);

try
{
cmd.Transaction = cnn.BeginTransaction();
cmd.CommandText = sqlString;
cmd.ExcuteNonQuery();
cmd.Transation.Commit();
}
catch(Exception e)
{
....
}

Answer 1

cnn先new实例化下看看

//str为数据库连接字符串
 DbConnection cnn = new MySqlConnection(str);