C# 如何验证ConnectionString是否存在，如果不存在，则不抛出错误 在应用程序配置中找不到连接名称“MySqlServer”，或者连接字符串为空。

因此，我有一个带有面板的页面，当在web配置中找到连接并且连接有效时，该页面将显示该面板；使用try/catch，只要add name“VALUE”在配置连接字符串中，如果服务器数据不正确，则将加载页面并将面板设置为不可见。。。我需要能够处理以下问题

如果aspx中使用了本例中的命名值MySqlServer；aspx.cs，但未在配置中找到，我不希望出现错误；找不到连接名称。。。。我只是不想像找到名称但数据不正确时SqlConnection.Open失败时那样显示面板

aspx

配置

<connectionStrings>
        <add name="NotMySqlServer" providerName="System.Data.SqlClient" connectionString="server=TEST\SQL2005;database=ADB;Integrated Security=True"/>
<add name="NotMy2SqlServer" providerName="System.Data.SqlClient" connectionString="server=TEST\SQL2005;database=ADB;Integrated Security=True"/>

    </connectionStrings>

---

您可以使用count检查是否存在任何连接字符串

var count = ConfigurationManager.ConnectionStrings.Count;
if (count > 0)
{
    //There is at least more then one connection string.
}

更新

public static class Extension
{
    public static bool HasConnectionString(this ConnectionStringSettingsCollection value, string key)
{
    try
    {
        return value[key].ConnectionString.Length > 0;
    }catch 
    {
        return false;
    }
}
}

您可以按如下方式使用扩展名

if (ConfigurationManager.ConnectionStrings.HasConnectionString("MySqlServer"))
{
    //If true you know there is a valid connectionstring.
}

您可以尝试：

if(ConfigurationManager.ConnectionStrings["MySqlServer"] == null) throw ...

---

如果您使用的是.NET 4.5+，并且有权访问C#6.0，则可以使用null条件运算符（

？

）尝试获取连接字符串，而不会自动引发异常：

string connectionString = ConfigurationManager.ConnectionStrings["MySqlServer"]?.ConnectionString;
//------------------------------------------------------------------------HERE-^-HERE-------------

if (string.IsNullOrWhiteSpace(connectionString))
{
    // Don't even bother trying to open the connection.
    // Log the error and either rethrow the exception (throw;) or exit from your current context (return;).
    //return;
    //throw;
}

// If your code has made it this far, it means you have a valid connection string.  Now try to use it.
using (var sqlConnection = new SqlConnection(connectionString))
{
    sqlConnection.Open();

    using (var sqlCommand = new SqlCommand)
    {
        // Do stuff.
    }
}

---

如何具体计算ConnectionString“name”=“MySqlServer”我认为最好检查：

string.IsNullOrWhiteSpace（连接字符串）

FYI:？是空条件运算符，而不是空合并运算符。请参阅：您完全正确--捕捉得很好。我更新了我的描述以合并该修复。

if(ConfigurationManager.ConnectionStrings["MySqlServer"] == null) throw ...

string connectionString = ConfigurationManager.ConnectionStrings["MySqlServer"]?.ConnectionString;
//------------------------------------------------------------------------HERE-^-HERE-------------

if (string.IsNullOrWhiteSpace(connectionString))
{
    // Don't even bother trying to open the connection.
    // Log the error and either rethrow the exception (throw;) or exit from your current context (return;).
    //return;
    //throw;
}

// If your code has made it this far, it means you have a valid connection string.  Now try to use it.
using (var sqlConnection = new SqlConnection(connectionString))
{
    sqlConnection.Open();

    using (var sqlCommand = new SqlCommand)
    {
        // Do stuff.
    }
}