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我已经搜索并尝试了所有方法，但无法弄清楚这一点。我正在尝试做一些简单的事情，但似乎我做错了什么。基本上，任何已经存款的用户，我想返回true，如果他们没有，我想返回false。我想这应该很容易，但我对此感到困惑。

这是错误：

ConnectionString 属性尚未初始化。

说明：执行当前 Web 请求期间发生未处理的异常。请查看堆栈跟踪以获取有关错误及其源自代码的位置的更多信息。

异常详细信息：System.InvalidOperationException：ConnectionString 属性尚未初始化。

源错误：

Line 59:         Cmd.Parameters.AddWithValue("@UserID", userId);
Line 60:         con.Open();
Line 61: 
Line 62:         result = (int)Cmd.ExecuteScalar();

这是堆栈跟踪的顶部：

[InvalidOperationException：ConnectionString 属性尚未初始化。] System.Data.SqlClient.SqlConnection.PermissionDemand() +4879939 System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection) +20 System.Data.ProviderBase.DbConnectionClosed.OpenConnection( DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122

这是我返回真假的方法：

public static bool HasDeposit(int userId)
{
    int result = 0;
    //since executeScalar is intended to retreive only a single value
    //from a query, we select the number of results instead of the email address
    //of each matching result.
    string queryTransaction = "SELECT COUNT(UserID) FROM Transaction WHERE TransactionTypeID = 6 AND UserID = @UserID";
    string constr = System.Configuration.ConfigurationManager.AppSettings["ConnectionString"];
    SqlConnection con = new SqlConnection(constr);

    SqlCommand Cmd = new SqlCommand(queryTransaction, con);

    Cmd.Parameters.AddWithValue("@UserID", userId);
    con.Open();

    result = (int)Cmd.ExecuteScalar();

    //returning a boolean comparator works like this :
    //will return true if the result is greater than zero, but false if it is not.
    con.Close();
    return result > 0;
}

对此的任何帮助/指导将不胜感激。

4

2 回答 2

12

如果您的配置中有这样的连接字符串

<connectionStrings>
    <add name="ConnectionString" connectionString="data source=.;Initial Catalog=MyDatabase;Integrated Security=SSPI" providerName="System.Data.SqlClient" />
</connectionStrings>

然后您将需要使用此方法来访问它System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString

您还应该将数据访问包装在 using 语句中，以免泄漏连接并淹没池。这是一个使用 using 语句的更新示例。

public static bool HasDeposit(int userId)
{
    //since executeScalar is intended to retreive only a single value
    //from a query, we select the number of results instead of the email address
    //of each matching result.
    const string queryTransaction = "SELECT COUNT(UserID) FROM Transaction WHERE TransactionTypeID = 6 AND UserID = @UserID";

    var constr = System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

    using (var con = new SqlConnection(constr))
    {
        using (var cmd = new SqlCommand(queryTransaction, con))
        {
            cmd.Parameters.AddWithValue("@UserID", userId);
            con.Open();

            var result = (int)cmd.ExecuteScalar();

            //returning a boolean comparator works like this :
            //will return true if the result is greater than zero, but false if it is not.
            return result > 0;
        }
    }
}
于 2013-08-17T01:34:20.383 回答
3

在 web.config 中：

<appSettings>
    <add key="ConnectionString" value="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"/>
</appSettings>
于 2013-08-17T01:39:21.130 回答