教训：System.TypeInitializationException 类型初始值设定项引发异常

在单元测试中出现了这个异常，原因是：
由于在测试项目中没有添加配置文件（只有前台网站项目中添加了 web.config）

//通过配置文件获取连接字符串
public static readonly string ConnectionStringLocalTransaction = ConfigurationManager.ConnectionStrings["MyPetShopConnection"].ConnectionString;

public static int ExecuteNonQuery(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
int result = cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
return result;
}

/// <summary>
/// 辅助函数
/// </summary>
/// <param name="cmd">命令对象</param>
/// <param name="conn">连接对象</param>
/// <param name="trans">事务对象</param>
/// <param name="cmdType">命令类型</param>
/// <param name="cmdText">命令字符串</param>
/// <param name="cmdParms">命令参数</param>
private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
{
if(conn.State != ConnectionState.Open)
conn.Open();

cmd.Connection = conn;
cmd.CommandText = cmdText;
cmd.CommandType = cmdType;

if (trans != null)
cmd.Transaction = trans;

if (cmdParms != null)
{
foreach (SqlParameter parm in cmdParms)
cmd.Parameters.Add(parm);
}
}

// 解决方法：添加App.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="MyPetShopConnection" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=E:\Web\MyPetShop\App_Data\MyPetShop.mdf;Integrated Security=True;User Instance=True"/>
</connectionStrings>
</configuration>

教训：如果类中存在静态成员，应确保其初始化时不会抛出异常，否则会影响对该类的正常访问
另外可以参考文章：

通过七个关键编程技巧得益于静态内容http://www.microsoft.com/china/MSDN/library/enterprisedevelopment/softwaredev/us0501StaticsinNET.mspx?mfr=true
内容转载于略作修改：/article/5683498.html