Question

我正在编写一个C＃应用程序，使用Dapper for ORM从MySQL数据库检索配方。到目前为止，我已经用C＃编写了直接查询的DAL（我知道这是不安全的），而且效果很好。我现在已经开始过渡到带有参数的存储过程，以更好地保护数据库免受SQL注入的侵扰，以及尽可能地使用最佳实践。

但是，当我同时使用Dapper的QueryAsync<T>（这也适用于Query<T>）和DynamicParameters时，出现了异常，消息为“数据为空。此方法或无法对Null值调用属性。”

但是，如果我以字符串文字SQL语句的形式执行查询，或者使用字符串文字来调用存储过程，则可以正常工作。我知道数据在那里，而不是null，因为当在MySQL中以我知道的ID号直接运行它时，它可以工作。我还尝试过使用我知道的id在C＃中运行下面列出的方法，其中一些工作正常，其中一些返回所述错误。

我不知道在进行QueryAsync<Recipe>("...")调用后哪里会失败。我不知道我提供给该方法的参数是否未传递到存储过程中，或者该过程是否返回null，或者如果出错则返回其他信息。

对于解决该呼叫失败的任何帮助，将不胜感激。我已经在底部包括了堆栈跟踪，到目前为止还没有任何意义。我仍然需要学习了解堆栈跟踪。

编辑： 我已经在SQL Server中重新创建了MySql数据库，并创建了一个新的DAL连接器。所有这些都完全反映了MySql结构和DAL。 GetRecipeByIdAsync1(int id)与SQL Server完全一样。因此，在Dapper / DynamicParameters / MySql.Data与MySQL中的存储过程进行交互的方式上肯定有一些东西。

我的食谱课：

public class Recipe
{

        [Description("id")]
        public int Id { get; set; }

        [Description("name")]
        public string Title { get; set; }

        [Description("description")]
        public string Description { get; set; }

        [Description("source_site")]
        public string SourceSite { get; set; }
}

这是我在MySQL中的recipes表：

recipes
=============
id (pk)     | INT          | Not Null   | Auto-Increment
name        | VARCHAR(45)  | Not Null   |
description | VARCHAR(250) | Allow Null |
source_site | VARCAHR(200) | Allow Null |

这是我用来设置自定义映射的帮助程序类，因此我的列无需与属性名称匹配：

public class Helper
{
    public static void SetTypeMaps()
    {
        var recipeMap = new CustomPropertyTypeMap(typeof(Recipe),
            (type, columnName) => type.GetProperties().FirstOrDefault(prop => GetDescriptionFromAttribute(prop) == columnName));

        SqlMapper.SetTypeMap(typeof(Recipe), recipeMap);

        // Other custom mappers omitted
    }

我正在使用的存储过程：

PROCEDURE `sp_recipes_GetByRecipeId`(IN RecipeId INT)
BEGIN
    SELECT r.*
    FROM recipes r
    WHERE r.id = RecipeId;
END

现在，我将在DAL中使用该方法的各种版本（为方便起见，在此已对其进行编号）：

/// This does not work
public async Task<Recipe> GetRecipeByIdAsync1(int id)
{
    using (IDbConnection db = new MySqlConnection(GlobalConfig.CnnString("CookbookTest1")))
    {
        var p = new DynamicParameters();
        p.Add("RecipeId", id, dbType: DbType.Int32, direction: ParameterDirection.Input);

        // This is the line where the exception occurs
        var result = await db.QueryAsync<Recipe>("sp_recipes_GetByRecipeId", p, commandType: CommandType.StoredProcedure); 

        return result.FirstOrDefault();
    }

}

// This also does not work
public async Task<Recipe> GetRecipeByIdAsync2(int id)
{
    using (IDbConnection db = new MySqlConnection(GlobalConfig.CnnString("CookbookTest1")))
    {
        // This is the line where the exception occurs
        var result = await db.QueryAsync<Recipe>("sp_recipes_GetByRecipeId", new {RecipeID = id}, commandType: CommandType.StoredProcedure); 

        return result.FirstOrDefault();
    }

}

// Nor this
public async Task<Recipe> GetRecipeByIdAsync3(int id)
{
    using (IDbConnection db = new MySqlConnection(GlobalConfig.CnnString("CookbookTest1")))
    {
        // This is the line where the exception occurs
        var result = await db.QueryAsync<Recipe>("sp_recipes_GetByRecipeId", new {id}, commandType: CommandType.StoredProcedure); 

        return result.FirstOrDefault();
    }

}

// This works perfectly, but I'm not sure how safe it is
public async Task<Recipe> GetRecipeByIdAsync4(int id)
{
    using (IDbConnection db = new MySqlConnection(GlobalConfig.CnnString("CookbookTest1")))
    {
        var result = await db.QueryAsync<Recipe>($"call sp_recipes_GetByRecipeId({id})"); 

        return result.FirstOrDefault();
    }

}

// And of course, this works, but is horrible practice
public async Task<Recipe> GetRecipeByIdAsync5(int id)
{
    using (IDbConnection db = new MySqlConnection(GlobalConfig.CnnString("CookbookTest1")))
    {
        var result = await db.QueryAsync<Recipe>($"SELECT * FROM recipes WHERE recipes.id = {id}"); 

        return result.FirstOrDefault();
    }

}

如果有人想要的话，连接字符串

<connectionStrings>
    <add name="CookbookTest1" connectionString="Server=localhost;Database=cookbook_test1;Uid=vs_dev;Pwd=developer;" providerName="MySql.Data"/>
</connectionStrings>

堆栈跟踪：

System.Data.SqlTypes.SqlNullValueException
  HResult=0x80131931
  Message=Data is Null. This method or property cannot be called on Null values.
  Source=MySql.Data
  StackTrace:
   at MySql.Data.MySqlClient.MySqlDataReader.GetFieldValue(Int32 index, Boolean checkNull)
   at MySql.Data.MySqlClient.MySqlDataReader.GetString(Int32 i)
   at MySql.Data.MySqlClient.MySqlDataReader.GetString(String column)
   at MySql.Data.MySqlClient.SchemaProvider.GetProcedures(String[] restrictions)
   at MySql.Data.MySqlClient.ISSchemaProvider.GetProcedures(String[] restrictions)
   at MySql.Data.MySqlClient.ISSchemaProvider.GetSchemaInternal(String collection, String[] restrictions)
   at MySql.Data.MySqlClient.SchemaProvider.GetSchema(String collection, String[] restrictions)
   at MySql.Data.MySqlClient.MySqlConnection.GetSchemaCollection(String collectionName, String[] restrictionValues)
   at MySql.Data.MySqlClient.ProcedureCache.GetProcData(MySqlConnection connection, String spName)
   at MySql.Data.MySqlClient.ProcedureCache.AddNew(MySqlConnection connection, String spName)
   at MySql.Data.MySqlClient.ProcedureCache.GetProcedure(MySqlConnection conn, String spName, String cacheKey)
   at MySql.Data.MySqlClient.StoredProcedure.GetParameters(String procName)
   at MySql.Data.MySqlClient.StoredProcedure.CheckParameters(String spName)
   at MySql.Data.MySqlClient.StoredProcedure.Resolve(Boolean preparing)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.ExecuteDbDataReaderAsync(CommandBehavior behavior, CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
   at Dapper.SqlMapper.<QueryAsync>d__33`1.MoveNext() in C:\projects\dapper\Dapper\SqlMapper.Async.cs:line 468
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at CookbookLibrary.DataAccess.MySqlConnector.<TestStoredProcAsync>d__5.MoveNext() in C:\Users\cyclone\Desktop\VS Projects\DigitalCookbook\CookbookLibrary\DataAccess\MySqlConnector.cs:line 119
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at DigitalCookbook.ViewModel.MainWindowModel.<TestProcedure>d__38.MoveNext() in C:\Users\cyclone\Desktop\VS Projects\DigitalCookbook\DigitalCookbook\ViewModel\MainWindowModel.cs:line 228
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at DigitalCookbook.ViewModel.MainWindowModel.<<get_TestCommand>b__31_0>d.MoveNext() in C:\Users\cyclone\Desktop\VS Projects\DigitalCookbook\DigitalCookbook\ViewModel\MainWindowModel.cs:line 114

Answer 1

这看起来像是Oracle的MySQL Connector / NET（也称为MySql.Data）中的错误。它看起来像我在该错误数据库中不熟悉的任何错误；它可能需要作为新的问题提交。（Bug 75301看起来很相似，但并不清楚是同一问题。）

我建议切换到MySqlConnector；它是MySQL的备用ADO.NET库，它与Dapper和MySQL Connector / NET中的fixes many known bugs兼容。 MySqlConnector还具有真正的异步I / O支持，在Connector / NET中为not implemented。如果您想在代码中使用QueryAsync，这将很重要。

更新：查看了Connector / NET源代码后，看来您的数据库中包含一些意外数据。以下两个查询之一是否产生行？如果是，NULL是哪个值？

SELECT * FROM information_schema.routines
WHERE specific_name IS NULL OR
    routine_schema IS NULL OR
    routine_name IS NULL OR
    routine_type IS NULL OR
    routine_definition IS NULL OR
    is_deterministic IS NULL OR
    sql_data_access IS NULL OR
    security_type IS NULL OR
    sql_mode IS NULL OR
    routine_comment IS NULL OR
    definer IS NULL;

SELECT * FROM mysql.proc
WHERE specific_name IS NULL OR
    db IS NULL OR
    name IS NULL OR
    type IS NULL OR
    body IS NULL OR
    is_deterministic IS NULL OR
    sql_data_access IS NULL OR
    security_type IS NULL OR
    sql_mode IS NULL OR
    comment IS NULL OR
    definer IS NULL;

您正在使用什么MySQL Server（MySQL，MariaDB，Amazon Aurora）以及哪个版本？

Dapper动态参数无效的C＃存储过程

1 个答案: