Entity Framework: Get Mapped Table Name from an Entity

Great post, hacking at its best! I just wanted to point out that the "<table>" in the Regex is a named capture group. That is why the next line works.

C#

match.Groups["table"].Value

I also changed the last line to return just the table name instead of "[dbo].[TableName]" to

C#

return match.Groups["table"].Value.Replace("[dbo].[", "").Replace("]", "");

modified 5-Nov-14 17:41pm.

I plan to add supplementary (unique) indexes to my entities' tables. Since I can't have more than one EF key for an entity, the other indexes need to be created using CONSTRAINT SQL, which in turns means converting between entity and property names (conceptual model) and table and column names (database store). I've taken the following code from another person (and converted it to VB):

Imports System.Data.Objects
Imports System.Data.Entity
Imports System.Data.SqlClient
Imports System.Data.EntityClient
Imports System.Data.Metadata.Edm
Imports System.Data.Objects.DataClasses
Imports System.Linq.Expressions
Imports System.Runtime.Serialization
Imports System.Reflection

Public Class ConvertConceptualToStore
    Private Shared Function GetTableName(Of T As EntityObject)() As String
    Dim type As Type = GetType(T)
    Dim at As EdmEntityTypeAttribute = GetAttribute(Of EdmEntityTypeAttribute)(type)
    Return at.Name
    End Function

    Private Shared Function GetColumnName(Of T As EntityObject) _
        (ByVal propertySelector As Expression(Of Func(Of T, Object))) As String

    If propertySelector Is Nothing Then
        Throw New Exception("""" &amp; propertySelector.ToString &amp; """ is null.")
    End If

    Dim propertyInfo As PropertyInfo = GetPropertyInfo(propertySelector.Body)
    Dim attribute As DataMemberAttribute = _
        GetAttribute(Of DataMemberAttribute)(propertyInfo)
    If String.IsNullOrEmpty(attribute.Name) Then
        Return propertyInfo.Name
    Else
        Return attribute.Name
    End If
    End Function

    Private Shared Function GetAttribute(Of T As Class)(ByVal memberInfo As MemberInfo) As T
    If memberInfo Is Nothing Then
        Throw New Exception("""" &amp; memberInfo.ToString &amp; """ is null.")
    End If

    Dim customAttributes() As Object = _
        memberInfo.GetCustomAttributes(GetType(T), False)
    Dim attribute As T = _
        DirectCast(customAttributes.Where(Function(a) TypeOf a Is T).First(), T)
    Return attribute
    End Function

    Private Shared Function GetPropertyInfo(ByVal propertySelector As Expression) As PropertyInfo
    If propertySelector Is Nothing Then
        Throw New Exception("""" &amp; propertySelector.ToString &amp; """ is null.")
    End If

    Dim memberExpression As MemberExpression = _
        TryCast(propertySelector, MemberExpression)
    If memberExpression Is Nothing Then
        Dim unaryExpression As UnaryExpression = _
            TryCast(propertySelector, UnaryExpression)
        If unaryExpression IsNot Nothing _
                AndAlso unaryExpression.NodeType = ExpressionType.Convert Then
            memberExpression = TryCast(unaryExpression.Operand, MemberExpression)
        End If
    End If
    If memberExpression IsNot Nothing _
            AndAlso memberExpression.Member.MemberType = MemberTypes.Property Then
        Return DirectCast(memberExpression.Member, PropertyInfo)
    Else
        Throw New ArgumentException("No property reference was found.", "propertySelector")
    End If
    End Function

    ' Invocation example
    Public Shared Sub Test()
    Dim table As String = GetTableName(Of Entity)()
    Dim column As String = GetColumnName(Of Entity)(Function(Location) Entity.Property)
    End Sub
End Class

I need to know some things:

1. I don't need an ObjectContext for this code, do I?
2. What if the property I need to convert to a field is part of a
complex property? Do I need to augment or modify the code for such a
situation? (i.e., Suppose I have an entity called Location, with a
complex property of Address, and I need to get the field for
Address.Street. Do I just use,
columnName = GetColumnName(Of Location)(Function(Location) Location.Address.Street),
or do I have to do something more?)
3. Suppose my code doesn't know beforehand the names of my entity and
property. Is there a way to adapt this code to take a _String value_
for each (at least for the property name; i.e., "Entity.Property"), then find the
appropriate class/property reference therefrom?

Please answer these questions ASAP!

Imports System.Data.Objects
Imports System.Data.Entity
Imports System.Data.SqlClient
Imports System.Data.EntityClient
Imports System.Data.Metadata.Edm

Public Class EFModelToDB
Public Shared Function GetTableName(Of T As Class)(ByVal context As ObjectContext) As String
Dim entitySet As EntitySet = GetEntitySet(Of T)(context)
If entitySet Is Nothing Then
Throw New Exception( _
"Unable to find entity set """ & GetType(T).Name & """ in edm metadata")
End If
Dim tableName As String = _
GetStringProperty(entitySet, "Schema") & "." & GetStringProperty(entitySet, "Table")
Return tableName
End Function

Private Shared Function GetEntitySet(Of T)(ByVal context As ObjectContext) As EntitySet
Dim type = GetType(T) : Dim entityName As String = type.Name
Dim metadata As MetadataWorkspace = context.MetadataWorkspace
Dim entitySets As IEnumerable(Of EntitySet) = _
From s In metadata.GetItemCollection(DataSpace.SSpace).GetItems(Of EntityContainer)() _
.Single().BaseEntitySets.OfType(Of EntitySet)()
Where (Not s.MetadataProperties.Contains("Type")) _
OrElse s.MetadataProperties("Type").ToString() = "Tables"
Dim entitySet As EntitySet = entitySets.FirstOrDefault(Function(e) e.Name = entityName)
Return entitySet
End Function

Private Shared Function GetStringProperty(ByVal entitySet As MetadataItem, _
ByVal propertyName As String) As String
Dim [property] As MetadataProperty = Nothing
If entitySet Is Nothing Then
Throw New ArgumentNullException("entitySet")
End If
If entitySet.MetadataProperties.TryGetValue(propertyName, False, [property]) Then
Dim str As String = Nothing : str = TryCast([property].Value, String)
If (([property] IsNot Nothing) AndAlso ([property].Value IsNot Nothing)) _
AndAlso ((str IsNot Nothing) AndAlso (Not String.IsNullOrEmpty(str))) Then
Return str
End If
End If
Return String.Empty
End Function
End Class

If you don't fancy parsing a SQL string,

C#

public string GetTableName<T>(DbContext context)
            where T: class
{
    var entitySet= GetEntitySet<T>(context);
    if (entitySet == null)
        throw new Exception("Unable to find entity set '{0}' in edm metadata".F(typeof(T).Name));
    var tableName = GetStringProperty(entitySet, "Schema") + "." + GetStringProperty(entitySet, "Table");
    return tableName;
}

private EntitySet GetEntitySet<T>(DbContext context)
{
    var type = typeof(T);
    var entityName = type.Name;
    var metadata = ((IObjectContextAdapter)context).ObjectContext..MetadataWorkspace;

    IEnumerable<EntitySet> entitySets;
    entitySets = metadata.GetItemCollection(DataSpace.SSpace)
                     .GetItems<EntityContainer>()
                     .Single()
                     .BaseEntitySets
                     .OfType<EntitySet>()
                     .Where(s => !s.MetadataProperties.Contains("Type")
                                 || s.MetadataProperties["Type"].ToString() == "Tables");
    var entitySet = entitySets.FirstOrDefault(t => t.Name == entityName);
    return entitySet;
}

private string GetStringProperty(MetadataItem entitySet, string propertyName)
{
    MetadataProperty property;
    if (entitySet == null)
        throw new ArgumentNullException("entitySet");
    if (entitySet.MetadataProperties.TryGetValue(propertyName, false, out property))
    {
        string str = null;
        if (((property != null) &&
            (property.Value != null)) &&
            (((str = property.Value as string) != null) &&
            !string.IsNullOrEmpty(str)))
        {
            return str;
        }
    }
    return string.Empty;
}

I'm using SqlBulCopy to do fast inserts, but getting the schema information from EF in a generic way.

This code is cobbled together from various places and tested it to the extent of my application requirements. The available code for using SqlBulkCopy in conjunction with EF seems a bit patchy, so hopefully this will assist anyone working in this area.

This is the VB 2010 version:

Imports System.Data.Objects
Imports System.Data.Entity
Imports System.Data.SqlClient
Imports System.Data.EntityClient
Imports System.Data.Metadata.Edm

Public Class EFModelToDB
	Public Shared Function GetTableName(Of T As Class)(ByVal context As ObjectContext) As String
	Dim entitySet As EntitySet = GetEntitySet(Of T)(context)
	If entitySet Is Nothing Then
		Throw New Exception( _
			"Unable to find entity set """ & GetType(T).Name & """ in edm metadata")
	End If
	Dim tableName As String = _
		GetStringProperty(entitySet, "Schema") & "." & GetStringProperty(entitySet, "Table")
	Return tableName
	End Function

	Private Shared Function GetEntitySet(Of T)(ByVal context As ObjectContext) As EntitySet
	Dim type = GetType(T) : Dim entityName As String = type.Name
	Dim metadata As MetadataWorkspace = context.MetadataWorkspace
	Dim entitySets As IEnumerable(Of EntitySet) = _
            From s In metadata.GetItemCollection(DataSpace.SSpace).GetItems(Of EntityContainer)() _
			.Single().BaseEntitySets.OfType(Of EntitySet)()
        	Where (Not s.MetadataProperties.Contains("Type")) _
			OrElse s.MetadataProperties("Type").ToString() = "Tables"
	Dim entitySet As EntitySet = entitySets.FirstOrDefault(Function(e) e.Name = entityName)
	Return entitySet
	End Function

	Private Shared Function GetStringProperty(ByVal entitySet As MetadataItem, _
		ByVal propertyName As String) As String
	Dim [property] As MetadataProperty = Nothing
	If entitySet Is Nothing Then
		Throw New ArgumentNullException("entitySet")
	End If
	If entitySet.MetadataProperties.TryGetValue(propertyName, False, [property]) Then
		Dim str As String = Nothing : str = TryCast([property].Value, String)
		If (([property] IsNot Nothing) AndAlso ([property].Value IsNot Nothing)) _
				AndAlso ((str IsNot Nothing) AndAlso (Not String.IsNullOrEmpty(str))) Then
			Return str
		End If
	End If
	Return String.Empty
	End Function
End Class

You can make a few tweaks to the Regex to also support Oracle. Oracle's ToTraceString() statement looks like:

VB

SELECT
"Extent1"."AlbumId" AS "AlbumId",
"Extent1"."GenreId" AS "GenreId",
"Extent1"."ArtistId" AS "ArtistId",
"Extent1"."Title" AS "Title",
"Extent1"."Price" AS "Price",
"Extent1"."AlbumArtUrl" AS "AlbumArtUrl"
FROM "DBO"."Albums" "Extent1"

So the Oracle Regex for Schema and Table would look like:

FROM "(?<schema>.*)"."(?<table>.*)"\s

Hi Mark,

Thanks for the tips! It's been a while since I worked with Oracle, I had no opportunity to use EF with Oracle. I'll try to update the article and source code in the next days.

Rui

Nice article!

You can also find the SQL Server schema using this Regex:

FROM [(?<schema>.*)].[(?<table>.*)] AS

Then you can wire up a method to extract the Schema as well as the Table.

Entity Framework: Get Mapped Table Name from an Entity

Table of Contents

The Problem

The Solution

The Extension Methods

Using the Code

References

License

Comments and Discussions