c# - “executenonquery连接属性尚未初始化”

SqlConnection cn = new SqlConnection(@"DataSource=dbedu.cs.vsb.cz\SQLDB;Persist Security Info=True;User ID=*****;Password=*******");

SqlCommand cmd = new SqlCommand();
string finish = DropDownListFi.SelectedValue;
cn.Open();
String Name = Request.QueryString["Name"];
cmd.CommandText = "UPDATE navaznost_ukolu SET finish=@finish where Name='" + Name + "'";
cmd.Parameters.Add(new SqlParameter("@finish", finish));
cmd.ExecuteNonQuery();
cmd.Clone();

错误讯息


  Executenonquery连接属性尚未初始化。

最佳答案

当前代码的问题是您尚未设置Connection对象的SqlCommand属性。尝试这个，

SqlCommand cmd = new SqlCommand();
cmd.Connection = cn;

并且还必须参数化name上设置的值

String Name = Request.QueryString["Name"];
cmd.CommandText = "UPDATE navaznost_ukolu SET finish=@finish where Name=@name";
cmd.Parameters.Add(new SqlParameter("@finish", finish));
cmd.Parameters.Add(new SqlParameter("@name", Name));

完整代码

string finish = DropDownListFi.SelectedValue;
String Name = Request.QueryString["Name"];
string connStr = @"DataSource=dbedu.cs.vsb.cz\SQLDB;
                   Persist Security Info=True;
                   User ID=*****;
                   Password=*******";
string sqlStatement = @"UPDATE navaznost_ukolu
                        SET    finish = @finish
                        WHERE  Name = @Name";

using (SqlConnection conn = new SqlConnection(connStr))
{
    using(SqlCommand cmd = new SqlCommand())
    {
        cmd.Connection = conn;
        cmd.CommandText = sqlStatement;
        cmd.CommandType = CommandType.Text;

        cmd.Parameters.Add(new SqlParameter("@finish", finish));
        cmd.Parameters.Add(new SqlParameter("@name", Name));

        try
        {
            conn.Open();
            cmd.ExecuteNonQuery();
        }
        catch(SqlException e)
        {
            // do something with the exception
            // do not hide it
            // e.Message.ToString()
        }
    }
}

为了正确编码


使用using语句处理适当的对象
使用try-catch块正确处理对象