在.net 4.5中有类似dbgeometry makevalid的东西吗？

Question

I'm trying to calculate area of polyline like that

    string poly = "POLYGON ((637604.918432772 2230520.64934531,
637622.257266129 2230419.44632915, 637279.107128549 2230192.04910755, 636765.470527745 2230179.6468564, 636778.005055813 2229861.77192838, 636529.81646905 2229464.29327025, 635813.486592791 2229523.30345774, 636017.385069448 2229974.32341381, 636267.323659164 2230070.32127916, 637035.026966561 2230404.70764784, 637275.265066307 2230401.13408429, 637604.918432772 2230520.64934531, 637604.918432772 2230520.64934531))";
     DbGeometry gm = DbGeometry.FromText(poly, 32637);
double area= gm.Area.Value; // here I got the error Exception has been thrown by the target of an invocation.

I noticed later that the reson of error that the dbgeometry is invalid I try the code in ms sql 2012 also give me the error but when I tried like that

SELECT @gm.MakeValid().STArea()

thats worked in sql my question is there is away to make the geometry valid in .net thank you

Answer 1

You definitely should not go to the DB to get what you want. A simple and fast method is to extend DbGeography by adding the following code to your project:

using System.Data.SqlTypes;
using Microsoft.SqlServer.Types;

namespace System.Data.Spatial
{
    public static class DbGeometryExtension
    {
        public static DbGeometry MakeValid(this DbGeometry geom)
        {
            if (geom.IsValid)
                return geom;

            return DbGeometry.FromText(SqlGeometry.STGeomFromText(new SqlChars(geom.AsText()), 4326).MakeValid().STAsText().ToSqlString().ToString(), 4326);

        }
    }
}

There are a few assumptions made when creating this code so don't use it "as is".

Answer 2

I'd agree with Bojan, unless you are using the Entity Framework?

The SqlGeometry object has a MakeValid() function, so using your example, allowing for a convert between DbGeography and SqlGeography:

DbGeography geog;
SqlGeometry geom = SqlGeometry.STGeomFromWKB(new SqlBytes(geog.AsBinary()), 32637);

However, unless you are using EF, I'd recommend simply using SqlGeometry as

1. There is no cast / conversion
2. SqlGeometry has far more functions available than DbGeometry.

Hope that helps.

Answer 3

SqlSpatialFunctions.MakeValid is a SQL Server-specific method to do that.

If you are interested why your geometry is invalid, you can ask SQL Server:

SELECT @gm.IsValidDetailed()

Also, you might want to consider using SQL Server geometry type directly: SqlGeometry.MakeValid .

Answer 4

here a medium solve to that problem that i make scallar function like that

CREATE FUNCTION [dbo].[GeomMakeValid](@geom as geometry)
RETURNS geometry
AS
BEGIN

DECLARE @gm as geometry;
set @gm = @geom.MakeValid();

return (@gm);
END

GO

then i call it from model like that

public static DbGeometry geoMakeValid(DbGeometry geom)
      {

          EntityConnection Connec = getConnection();

          DbCommand com = Connec.StoreConnection.CreateCommand();
          com.CommandText = "select dbo.GeomMakeValid(@geom)";
          com.CommandType = System.Data.CommandType.Text;
          com.Parameters.Add(new SqlParameter("@geom", geom.AsText()));
          if (com.Connection.State == ConnectionState.Closed) com.Connection.Open();
          try
          {
              var result = com.ExecuteScalar(); // should properly get your value
              Connec.Close();
              return DbGeometry.FromText( result.ToString(),geom.CoordinateSystemId);

          }
          catch (System.Exception e)
          {

          }
          Connec.Close();
          return geom;
      }

any any part of code i can call this function to make geometry valid