How to traverse a dacpac

Question

We are looking to upgrade our dbproj to a sqlproj so that we can point it to a new SQL 2012 database. We have a program at the moment that reads the .dbschema xml file to find all tables and columns and retrieve information from them. We use this data to build our own custom classes.

The new sqlproj file now produces a dacpac which we want to interrigate to get out the data that we need. I have written the following to try and traverse the dacpac and get the information that I need:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.SqlServer.Dac;
using Microsoft.SqlServer.Dac.Extensions;
using Microsoft.SqlServer.Dac.Model;
namespace DacPacReader
{
    class Program
    {
        static void Main(string[] args)
        {
            using (System.IO.TextWriter writter = new System.IO.StreamWriter(@"c:\temp\output.txt"))
            {
                using (TSqlModel model = new TSqlModel(@"C:\temp\Data.dacpac"))
                {
                    var allTables = model.GetObjects(DacQueryScopes.All, ModelSchema.Table);

                    foreach (var table in allTables)
                    {
                        writter.WriteLine(table.Name);
                        foreach (var column in table.GetChildren().Where(child => child.ObjectType.Name == "Column"))
                        {
                            writter.WriteLine("\t" + column.Name);
                            writter.WriteLine("\tProperties:");
                            foreach (var property in column.ObjectType.Properties)
                            {
                                writter.WriteLine("\t\t" + property.Name + "\t\t" + property.DataType.FullName);
                            }
                            writter.WriteLine("\tMetadata:");
                            foreach (var metaData in column.ObjectType.Metadata)
                            {
                                writter.WriteLine("\t\t" + metaData.Name + "\t\t" + metaData.DataType.FullName);
                            }
                        }
                    }
                }
            }
        }
    }
}

I have no idea if I'm doing this the right way, or if there is a much better/easier way. I'm not sure what to search for on Google/S.E. and can't find any examples.

I can see that the variable column has a non-public member called ContextObject which is a Microsoft.Data.Tools.Schema.Sql.SchemaModel.SqlSimpleColumn. If I could access this object then I would be able to pull all the info I needed out of it. Table also has a similar ContextObject which would help me.

Anyway, currently this opens the dacpac and retrieves all of the table and column names. An example of the data I get is:

[dbo].[User]
    [dbo].[User].[UserID]
    Properties:
        Collation       System.String
        IsIdentityNotForReplication     System.Boolean
        Nullable        System.Boolean
        IsRowGuidCol        System.Boolean
        Sparse      System.Boolean
        Expression      Microsoft.Data.Tools.Schema.Sql.SchemaModel.SqlScriptProperty
        Persisted       System.Boolean
        PersistedNullable       System.Nullable`1[[System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]
        Scale       System.Int32
        Precision       System.Int32
        Length      System.Int32
        IsMax       System.Boolean
        XmlStyle        Microsoft.SqlServer.Dac.Model.XmlStyle
        IdentityIncrement       System.String
        IdentitySeed        System.String
        IsFileStream        System.Boolean
        IsIdentity      System.Boolean
    Metadata:
        ColumnType      Microsoft.SqlServer.Dac.Model.ColumnType

Basically, I'd like to do one of the following:

1. Access the ContextObject to get a Microsoft.Data.Tools.Schema.Sql.SchemaModel.* object OR
2. Get the value of the property and metadata from the ObjectType properties OR
3. Start from scratch with an easier way to get this information out

We need to get information out such as the column type, howif it's nullable, and the scale and precision of a column

Answer 1

So, there is a fully-defined set of metadata classes that you can use when querying the model. This is simpler than relying on Linq and needing to test the string names of each property. See Table and Column classes for an example. I've updated your example showing how these are used:

// Query for UserDefined objects to just filter to your own objects. All will
// include system objects (references to objects in master.dacpac if you reference that
// and BuiltIn objects such as the data types. You probably don't care about those
var allTables = model.GetObjects(DacQueryScopes.UserDefined, Table.TypeClass);

foreach (var table in allTables)
{
    writter.WriteLine(table.Name);
    // Columns are referenced by tables, so GetReferenced can be used. The GetChildren can also be used 
    // but filtering by comparing "child.ObjectType == Column.TypeClass" would simplify your example
    foreach (var column in table.GetReferenced(Table.Columns))
    {
        // Now you can use the Column metadata class's properties to query your Column object
        bool isNullable = column.GetProperty<bool>(Column.Nullable); 
        SqlDataType sdt = column.GetReferenced(Column.DataType).First().GetProperty<SqlDataType>(DataType.SqlDataType);
    }

Answer 2

The way that we have found to do it is to find the property in object type using Linq, and then using the GetProperty method to get the value:

bool isNullable = (bool)column.GetProperty(column.ObjectType.Properties.Where(p => p.Name == "Nullable").First());

This still doesn't feel like the best option, so if someone else has a better answer please post it.