c# - 在控制台应用程序中定义连接字符串

Question

我正在尝试创建连接，但是它始终采用null。 下面我提到一种方法，我是如何做到的:

程序.cs:

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["CreateConnection"].ConnectionString);

应用程序配置:

<configuration>

   <connectionStrings>
    <add name="CreateConnection" connectionString="data source=MyDatabase;initial catalog=TestDatabase;integrated security=True;MultipleActiveResultSets=True;user id=ABC;password=Admin@123;App=EntityFramework;" providerName="System.Data.EntityClient" />
   </connectionStrings>

</configuration>

Answer 1

我使用了以下方式。检查这是否有帮助用于 MySQL

在App.config文件中

<appSettings>
  <add key="DBConnectionString" 
   value="server=localhost;userid=root;database=databasename"/>
  </appSettings> 

在Program.cs中

public static string m_strMySQLConnectionString;
static MySqlConnection m_mySqlConnection;

static void Main(string[] args)
{
  m_strMySQLConnectionString = ConfigurationManager.AppSettings["DBConnectionString"].ToString();
  m_mySqlConnection = null;
 }

在数据库助手函数中

public string GetValueFromDB(string strQuery)
    {
        string strData = "";

        try
        {
            if (m_mySqlConnection == null)
                OpenDatabase();

            if (string.IsNullOrEmpty(strQuery) == true)
                return string.Empty;

            MySqlCommand cmd = new MySqlCommand(strQuery, m_mySqlConnection);
            object objValue = cmd.ExecuteScalar();
            if (objValue == null)
            {
                cmd.Dispose();
                return string.Empty;
            }
            else
            {
                strData = (string)cmd.ExecuteScalar();
                cmd.Dispose();
            }

            if (strData == null)
                return string.Empty;
            else
                return strData;
        }
        catch (MySqlException ex)
        {
            LogException(ex);
            return string.Empty;
        }
        catch (Exception ex)
        {
            LogException(ex);
            return string.Empty;
        }
        finally
        {
            CloseDatabase();
        }
    }