使用Dapper从T-SQL存储过程返回XML字符串 [英] Using Dapper to return XML string from T-SQL stored procedures

问题描述

我正在一个项目中，将大型VB6应用程序转换为.NET。我决定创建一个项目，为现有的VB6 ADO代码提供外观，在这里我使用令人惊叹的Dapper扩展方法来处理VB6 ADO函数用来完成的所有数据库代码。

I am working on a project to convert a large VB6 application to .NET. I decided to create a project to provide a facade to the existing VB6 ADO code, where I am using the amazing Dapper extension methods to handle all the database code that the VB6 ADO functions used to do.

我在新项目中必须支持的功能之一是能够（通过FOR XML）从T-SQL存储过程中获取XML字符串结果。 Dapper不支持返回我可以看到的XML。因此，我实现了ADO.NET ExecuteXmlReader 方法来提供此返回值。我的项目还使用Dapper DynamicParameters 捕获存储过程所需的所有输入/输出参数。

One of the features I have to support in my new project is the ability to get the XML string results from T-SQL stored procedures (via the FOR XML). Dapper doesn't have support to return this XML that I can see. So, I implemented the ADO.NET ExecuteXmlReader method to provide this return. My project is also using Dapper DynamicParameters to capture all the in/out parameters required for the stored procedures.

我不知道怎么做，是如何将 DynamicParameters 转换为 SqlCommand.SqlParameterCollection ，这样我就可以将这些参数填充到 ExecuteXmlReader SqlCommand 对象中c>方法。对于这种情况，我也必须支持输出参数。

What I don't see how to do, is how to convert the DynamicParameters to the SqlCommand.SqlParameterCollection so that I can populate these parameters into the SqlCommand object for the ExecuteXmlReader method. I have to support output parameters also for this scenario.

我可以遍历 DynamicParameters ，但是那只能得到参数名称和值。我还需要方向，类型，大小，比例和精度。 Dapper有一个 DynamicParameters.ReplaceLiterals 方法，该方法采用 IDbCommand 对象替换SQL字符串中的文字。我希望它有一种也可以填写参数的方法。

I can iterate over the DynamicParameters, but that only gets me the parameter name, and value. I also need the direction, type, size, scale, and precision. Dapper has a DynamicParameters.ReplaceLiterals method that takes an IDbCommand object for replacing literals in SQL string. I wish it had a method to also fill in the parameters.

我在这里错过了明显的东西吗？如果我调用Dapper Execute 方法，则可以将 DyanmicParameters 直接传递给此方法。我只是看不到如何将它们传递给 SqlCommand 对象。

Am I missing something obvious here? If I call the Dapper Execute method, I can pass the DyanmicParameters directly into this method. I'm just not seeing how to pass them to the SqlCommand object.

推荐答案

经过测试，我发现Dapper确实支持从存储过程中提取XML。

After testing, I see that Dapper does indeed support pulling the XML from stored procedures.

var result = conn.Query<string>(@"select * from <someTable> for xml auto");

这将返回一个字符串数组，每个元素最多包含2,033个字符，您可以简单地加入

This will return an array of string with each element containing up to 2,033 characters, which you can simple join to have your result as a single string.

var fullResult = string.Join("", result);

或

var fullResult = string.Concat(result);

或全部一步：

var result = string.Concat(conn.Query<string>(
    @"select * from <someTable> for xml auto", buffered: false));

因此，我不需要自己实现ExcuteXmlReader方法，现在我可以让Dapper处理参数通常。

So, there is no need for me to implement ExcuteXmlReader method myself, and now I can let Dapper handle the parameters normally.

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