在運行時更改實體模型數據庫

Question

如何在運行時切換實體模型所連接的數據庫？

如果我有培訓數據庫和生產數據庫，例如，如何通過更改應用程序中的設置來使我的應用程序在兩者之間切換。

Answer 1

賈斯汀Pihony有正確的答案。 如果您想要同時訪問兩個數據庫（來回切換）而不是更改配置並重新啓動應用程序.....那麼您有兩個設置一個用於Train和一個用於Prod，然後執行您的上下文，如下所示：

string training = ConfigurationManager.ConnectionStrings["Train"].ToString(); 
string production = ConfigurationManager.ConnectionStrings["Prod"].ToString(); 

..... 
EFContext context = null; 
if (InTraining) 
    context = new EfContext(training); 
else 
    context = new EfContext(production); 

Answer 2

通常這是通過配置文件設置完成的。 Here is the MSDN on EF connection strings和here is some more info on it, basically saying it should be in your app.config

而且，如果你想從代碼的東西，here is a code project：

string connectionString = new System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"]); 

System.Data.SqlClient.SqlConnectionStringBuilder scsb = new System.Data.SqlClient.SqlConnectionStringBuilder(connectionString); 

EntityConnectionStringBuilder ecb = new EntityConnectionStringBuilder(); 
ecb.Metadata = "res://*/Sample.csdl|res://*/Sample.ssdl|res://*/Sample.msl"; 
ecb.Provider = "System.Data.SqlClient"; 
ecb.ProviderConnectionString = scsb.ConnectionString; 

dataContext = new SampleEntities(ecb.ConnectionString);