使用带有 SQL 空间类型的 Dapper 作为参数 [英] Using Dapper with SQL Spatial Types as a parameter

问题描述

我有一个系统，它基本上必须执行这样的查询:

I've got a system which basically has to do a query like this:

SELECT * FROM MyTable WHERE @parameter.STIntersects(MyGeometryColumn)

这在使用普通 SQL 参数时非常简单，您只需以非典型方式创建参数(其中 builder 变量是我用来创建矩形的 SqlGeometryBuilder):

This is quite simple to do when using vanilla SQL parameters, you just have to create your parameter in a non-typical way (where the builder variable is a SqlGeometryBuilder which I use to create a rectangle):

command.Parameters.Add(new SqlParameter
{
    UdtTypeName = "geometry",
    Value = builder.ConstructedGeometry,
    ParameterName = "@paremeter"
});

现在，当我尝试使用 dapper 执行此操作时，我收到一个错误，提示它无法弄清楚如何将其用作参数.任何人都有这个工作，或者有关如何启用它的任何指示?我确实有一个解决方法，但这涉及使用字符串表示并将其转换为我的 SQL 查询中的几何类型.我真的不想那样.

Now, When I try to do this using dapper, I get an error that it can't figure out how to use this as a parameter. Anyone who has got this working, or any pointers on how to enable this? I do have a workaround, but that involves using the string representation and converting that to a geometry type in my SQL query. I really don't want that.

为了回答评论，我得到的错误是Microsoft.SqlServer.Types.SqlGeometry 类型的成员参数不能用作参数值".换句话说，dapper 不知道如何处理 SqlGeometry 对象作为参数.

To answer the comment, the error I'm getting is 'The member Parameter of type Microsoft.SqlServer.Types.SqlGeometry cannot be used as a parameter value'. In other words, dapper doesn't know how to deal with a SqlGeometry object as a parameter.

推荐答案

实现奇葩的 DB 特定参数的关键都归结为 SqlMapper.IDynamicParameters

The key to implementing weird and wonderful DB specific params all boils down to SqlMapper.IDynamicParameters

这个简单的接口只有一个端点:

This simple interface has a single endpoint:

public interface IDynamicParameters
{
    void AddParameters(IDbCommand command);
}

Dapper 已经有这个接口的 DB 通用实现，称为:DynamicParameters，它允许您处理输出和返回值.

Dapper already has a DB generic implementation of this interface called: DynamicParameters which allows you to handle output and return values.

为了模拟这个空间的东西，我会尝试类似的东西:

To emulate this spatial stuff I would try something like:

public class SpatialParam : SqlMapper.IDynamicParameters
{
    string name; 
    object val;

    public SpatialParam(string name, object val)
    {
       this.name = name; 
       this.val = val;
    }

    public void AddParameters(IDbCommand command, SqlMapper.Identity identity)
    {
       var sqlCommand = (SqlCommand)command;
       sqlCommand.Parameters.Add(new SqlParameter
       {
          UdtTypeName = "geometry",
          Value = val,
          ParameterName = name
       });
    }
}

用法:

cnn.Query("SELECT * FROM MyTable WHERE @parameter.STIntersects(MyGeometryColumn)",
  new SpatialParam("@parameter", builder.ConstructedGeometry));

<小时>

这个简单的接口实现只处理一个参数，但它可以很容易地扩展到处理多个参数，无论是通过从构造函数传入还是添加一个辅助的 AddParameter 方法.

---

This simple implementation of the interface handles only a single param, but it can easily be extended to handle multiple params, either by passing in from the constructor or adding a helper AddParameter method.

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