如何解决这个错误？

Question

嗨，我尝试做在像父和子（表）的树视图中实现数据库记录。在运行时我在连接字符串中遇到错误..

错误行： -

string connectionstring = ConfigurationManager.ConnectionStrings["Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True"].ConnectionString; 

错误是： -

System.NullReferenceException was unhandled by user code 
    Object reference not set to an instance of an object. 

注：-in我的数据库没有字段为空

代码： -

string connectionstring = ConfigurationManager.ConnectionStrings["Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True"].ConnectionString; 
SqlConnection mycon = new SqlConnection(connectionstring); 
mycon.Open(); 
SqlCommand mycmd = new SqlCommand("Select * from tbl_Parent", mycon); 
SqlDataReader dr = mycmd.ExecuteReader(); 
mycmd.Dispose(); 
string[,] ParentNode = new string[100, 2]; 
int count = 0; 
while (dr.Read()) 
{ 
    ParentNode[count, 0] = dr.GetValue(dr.GetOrdinal("Parent_id")).ToString(); 
    ParentNode[count++, 1] = dr.GetValue(dr.GetOrdinal("Parent_name")).ToString(); 
} 
dr.Close(); 

Answer 1

您的连接字符串行不正确。它正在寻找在web.config中名为

"Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True". 

由于该节点（显然）不存在，它返回null和你得到一个异常的节点。

我怀疑你只是想：

string connectionstring = "Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True"; 

但是，如果没有更多的情况下，我不能知道。

Answer 2

更换

string connectionstring = ConfigurationManager.ConnectionStrings["Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True"].ConnectionString; 

随着

string connectionstring = "Data Source=ASDF;Initial Catalog=dbtree;Integrated Security=True"; 

或者使用连接字符串名称

string connectionstring = ConfigurationManager.ConnectionStrings["Name here"].ConnectionString; 

更新：由于评论者以下建议，你可以找到在网络的连接字符串的名称.config文件。