C# 在app.config之外的实体框架中为PostgreSQL数据库设置connectionString

我用PostgreSQL构建了一个数据库，我通过EntityFramework6访问它

直到最近，它还在

app.config

connectionString中平稳运行：

<connectionStrings>
    <add
        name="fancyName"
        connectionString="Host=localhost; user id=allCanSee; password=notSoSecret; database=notHidden"
        providerName="Npgsql" />
</connectionStrings>

但是由于我的

app.config

不再包含connectionString，我必须告诉数据库在哪里查找

我目前的尝试是这样的：

public static class VersionContextConnection
{
    public static string GetConnectionString() //Accessable form everywhere
    {
        var providerName = "Npgsql";
        var databaseName = decryptedName;
        var userName = decryptedUserName;
        var password = decryptedPassword;
        var host = decryptedHostName
        var port = 5432;

        return $"Provider={providerName}; " + $"Server={host}; " + $"Port={port}; " + 
            $"User Id={userName}; " + $"Password={password}; " + $"Database={databaseName};";
    }
}

public class VersionContext : DbContext
{
    public virtual DbSet<DatabaseNumber> DatabaseVersion { get; set; }

    public VersionContext() : base(VersionContextConnection.GetConnectionString())
    {
        System.Data.Entity.Database.SetInitializer<DatabaseContext>(null);
    }
}

但是这给了

系统一个例外。数据
说
关键字不受支持：“提供者”。

从connectionString中删除
提供程序会出现另一个异常：
关键字不受支持：“端口”。

从connectionString中删除
端口
会导致
.Net SqlClient数据提供程序
中的第三个异常：
用户“secretSecret”登录失败。

因此-如果未通过
：base（connectionString）
属性设置connectionString，如何设置connectionString？
您可以尝试使用EntityConnectionStringBuilder：

将静态方法修改为：

public static string GetConnectionString() //Accessable form everywhere
{
       var providerName = "Npgsql";
       var databaseName = decryptedName;
       var userName = decryptedUserName;
       var password = decryptedPassword;
       var host = decryptedHostName;
       var port = 5432;

       // Initializing the connection string builder for the provider
       SqlConnectionStringBuilder sqlBuilder = new SqlConnectionStringBuilder();
       sqlBuilder.ConnectionString = String.Format("Host={0};user id={1},password={2},database={3}",
       host, userName, password, databaseName);

       // Initialize the EntityConnectionStringBuilder.
       EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
       entityBuilder.Provider = providerName;
       entityBuilder.ProviderConnectionString = sqlBuilder.ToString();

       return entityBuilder.ToString();
}

并添加using语句：
using System.Data.SqlClient和
顺便问一下，支持端口吗？在您首先显示的connectionString中，没有端口参数。
从中出现了一个解决方案

app.config
包含以下提供程序：

<providers>
    <provider 
        invariantName="Npgsql" <!-- this is what we need -->
        type="Npgsql.NpgsqlServices, EntityFramework6.Npgsql" />
</providers>

将
DbContext
设置为：

public class VersionContext : DbContext
{
    public virtual DbSet<DatabaseNumber> DatabaseVersion { get; set; }

    public VersionContext() : base(VersionContextConnection.GetDatabaseConnection(), true)
    {
        System.Data.Entity.Database.SetInitializer<DatabaseContext>(null); 
    }
}

有了这些，你可以用加密的登录参数填充你的
app.config
，检索它们，并将它们传递给你的
DbContext
，这就是我能做的

    public static DbConnection GetDatabaseConnection()
    {
      
        NpgsqlConnectionStringBuilder npgsqlConnectionStringBuilder = new NpgsqlConnectionStringBuilder();
        npgsqlConnectionStringBuilder.Host = "localhost";
        npgsqlConnectionStringBuilder.Port = 5432;
        npgsqlConnectionStringBuilder.Database = "database";
        npgsqlConnectionStringBuilder.Username = "postgres";
        npgsqlConnectionStringBuilder.Password = "postgres";

        var conn = new NpgsqlConnectionFactory().CreateConnection(npgsqlConnectionStringBuilder.ConnectionString.ToString());
        return conn;
    }

在运行时设置它怎么样？像这样的@Forlani这是一个解决方案，但是密码和用户名将在运行时公开……或者，它应该是server:port吗？而不是服务器；port？我不久前试过，@Forlani，但它也导致了en异常，它说它在
entityBuilder
中缺少
metadata
。我没有元数据可以提供，我尝试的结果是出现了更多的异常，这些异常没有使用npgsql进行连接。然而，我找到了一个解决方案（参见线程）。
public static class VersionContextConnection
{
    public static DbConnection GetDatabaseConnection()
    {
        var providerName = "Npgsql"; //Get this
        var databaseName = decryptedDatabaseName;
        var userName = decryptedUserName;
        var password = decryptedPassword;
        var host = decryptedHostName
        var port = 5432;

        //Insert it here
        var conn = DbProviderFactories.GetFactory(providerName).CreateConnection(); 
        conn.ConnectionString = $"Server={host}; " + $"Port={port}; " + 
            $"User Id={userName};" + $"Password={password};" + $"Database={databaseName};";

        return conn;
    }
}

public class VersionContext : DbContext
{
    public virtual DbSet<DatabaseNumber> DatabaseVersion { get; set; }

    public VersionContext() : base(VersionContextConnection.GetDatabaseConnection(), true)
    {
        System.Data.Entity.Database.SetInitializer<DatabaseContext>(null); 
    }
}

using (var context = new VersionContext())
{
    var entry = context.DatabaseVersion.FirstOrDefault();
    ...
}

    public static DbConnection GetDatabaseConnection()
    {
      
        NpgsqlConnectionStringBuilder npgsqlConnectionStringBuilder = new NpgsqlConnectionStringBuilder();
        npgsqlConnectionStringBuilder.Host = "localhost";
        npgsqlConnectionStringBuilder.Port = 5432;
        npgsqlConnectionStringBuilder.Database = "database";
        npgsqlConnectionStringBuilder.Username = "postgres";
        npgsqlConnectionStringBuilder.Password = "postgres";

        var conn = new NpgsqlConnectionFactory().CreateConnection(npgsqlConnectionStringBuilder.ConnectionString.ToString());
        return conn;
    }