[英]Why am I getting this error: The ConnectionString property has not been initialized
我已經搜索並嘗試了所有的東西,但無法想出這個。 我想做一些簡單的事情,但好像我做錯了什么。 基本上,任何已存款的用戶,我想返回true,如果他們沒有,我想返回false。 我想這應該很容易,但我對此感到難過。
這是錯誤:
ConnectionString屬性尚未初始化。
描述:執行當前Web請求期間發生未處理的異常。 請查看堆棧跟蹤以獲取有關錯誤及其源自代碼的位置的更多信息。
異常詳細信息:System.InvalidOperationException:尚未初始化ConnectionString屬性。
來源錯誤:
Line 59: Cmd.Parameters.AddWithValue("@UserID", userId);
Line 60: con.Open();
Line 61:
Line 62: result = (int)Cmd.ExecuteScalar();
這是堆棧跟蹤的頂部:
[InvalidOperationException:ConnectionString屬性尚未初始化。] 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
這是我返回true或false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;
}
任何關於此的幫助/指導將非常感激。
如果您的配置中有連接字符串,請執行此操作
<connectionStrings>
<add name="ConnectionString" connectionString="data source=.;Initial Catalog=MyDatabase;Integrated Security=SSPI" providerName="System.Data.SqlClient" />
</connectionStrings>
然后,您將需要使用此方法來訪問它System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString
您還應該在using語句中包裝數據訪問,這樣就不會泄漏連接並使池泛濫。 這是使用語句的更新示例。
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;
}
}
}
在web.config中:
<appSettings>
<add key="ConnectionString" value="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"/>
</appSettings>
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