错误ExecuteNonQuery：连接属性尚未初始化，当我单击插入按钮

Question

我一直试图使用C＃语言将数据从Visual Studio添加到SQL服务器，但它显示错误，当我按下添加按钮。连接类如下所示：

class Globalconnection 
{ 
    public static SqlConnection cn; 
    public static string strServer = ""; 
    public static string strDatabase = ""; 
    public static string strUID = ""; 
    public static string strPWD = ""; 

    public static void SetupConnection() 
    { 
     cn = new SqlConnection("Server=" + strServer + "; Database=" + strDatabase + "; UID=" + strUID + ";PWD=" + strPWD); 
     cn.Open(); 
    } 
} 

在这个类中，大多数SQL命令都是为了将​​数据插入SQL而给出的。

class DACLASS 
{ 
    public static string strUID = ""; 
    public static string strPWD = ""; 
    public static string strNPWD = ""; 
    public static DataTable AccessData() 
    { 
     SqlDataAdapter da = new SqlDataAdapter("Select * from Users where Username='" + strUID + "' and Password='" + strPWD + "'", Globalconnection.cn); 
     DataSet ds = new DataSet(); 
     da.Fill(ds, "USERS"); 
     return ds.Tables[0]; 
    } 

    public static void addStatue(string ID, string Name) 
    { 
     string strAddStatue = "Insert into Statues VALUES (@ID, @Name)"; 

     SqlCommand cmdAddStatue = new SqlCommand(strAddStatue, Globalconnection.cn); 

     cmdAddStatue.Parameters.AddWithValue("@ID", ID); 
     cmdAddStatue.Parameters.AddWithValue("@Name", Name); 
     cmdAddStatue.ExecuteNonQuery(); 
    } 
} 

以下命令来自“ADD”按钮。

private void txtADD_Click(object sender, EventArgs e) 
{ 
    try 
    { 
     if (txtID.Text == "" || txtName.Text == "" || txtSize.Text == "" || txtTCP.Text == "" || txtMP.Text == "") 
     { 
      MessageBox.Show("ID, Name, Size, Total Cost Price and Marked Price are Mandatory", "Handicrafts"); 
     } 
     else 
     { 
      DACLASS.addStatue(txtID.Text, txtName.Text); 
      MessageBox.Show("Statue Added", "Handicraft"); 
      btnClear_Click(sender, e); 
     } 
    } 
    catch (Exception ex) 
    { 
     MessageBox.Show(ex.Message, "Handicrafts"); 
     btnClear_Click(sender, e); 
    } 
} 

当我把空值显示在消息框，但是当我插入正确的价值观，我得到这个错误

的ExecuteNonQuery：Connection属性尚未初始化

Answer 1

添加此行你的构造函数，或绝望的txtADD_Click（）方法

Globalconnection.SetupConnection(); 

你已经做好了所有的工作，向计算机解释如何打开连接，你只是从来没有真正告诉它要做到这一点:)

希望它可以帮助..

Answer 2

它似乎像你从来没有实际上运行了GlobalConnection类中的设置连接方法。也许你会更好地实现你的sql连接的单例模式。

Answer 3

您需要打开SqlConnection，然后从SqlCommand的实例调用ExecuteNonQuery方法。致电ExecuteNonQuery后，SqlConnection必须关闭。我建议改变Globalconnection如下

class Globalconnection 
{ 
    public static string strServer = ""; 
    public static string strDatabase = ""; 
    public static string strUID = ""; 
    public static string strPWD = ""; 
    public static SqlConnection cn = new SqlConnection("Server=" + strServer + "; Database=" + strDatabase + "; UID=" + strUID + ";PWD=" + strPWD); 
} 

然后用using statement内addStatue方法，以确保执行cmdAddStatue后SqlConnection关闭。

public static void addStatue(string ID, string Name) 
{ 
    string strAddStatue = "Insert into Statues VALUES (@ID, @Name)"; 

    using (var connection1 = Globalconnection.cn) 
    { 
     using (var cmdAddStatue = new SqlCommand(strAddStatue, connection1)) 
     { 
      cmdAddStatue.Parameters.AddWithValue("@ID", ID); 
      cmdAddStatue.Parameters.AddWithValue("@Name", Name); 

      connection1.Open(); 
      cmdAddStatue.ExecuteNonQuery(); 
     } 
    } 
}