I want to enforce Unique constraint in a table & I am using Entity Framework Code-First.
Is it possible to add a unique constraint using EF 6 as i believe in earlier versions it was not possible.
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See this Q -> stackoverflow.com/questions/21573550/…SBirthare– SBirthare2014-11-10 06:11:47 +00:00Commented Nov 10, 2014 at 6:11
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3 Answers
It appears that the unique constraint feature that was scheduled to release with Version 6 got pushed to 6.1.
With EF 6.1, you can define a constraint using the Index attribute as shown below:
[Index("IX_FirstAndSecond", 1, IsUnique = true)]
public int FirstColumn { get; set; }
[Index("IX_FirstAndSecond", 2, IsUnique = true)]
public int SecondColumn { get; set; }
OR
You can use Fluent API as shown here in MSDN
7 Comments
subi_speedrunner
Thanks for the Update,so creating this unique index has the same effect as of creating unique constraint
Shimmy Weitzhandler
Can't seem to find it in EF7 - DNX.
Rolf
@Shimmy Indexes can not be created using data annotations in EF7.
Mike Smith - MCT
"IX_" is just a convention used in SQL Server. For example, "PK_" is the common prefix for a primary key index.
dbardakov
IX_ is used for non-unique index, for unique it's UX_ |
Let's say that you want to add the Unique constraint on only one attribute, you can do as following, starting from EF6.1
[Index(IsUnique = true)]
public string Username { get; set; }
If you have multiple fields that are related to the same index then you are going to use:
Multiple-Column Indexes
Indexes that span multiple columns are specified by using the same name in multiple Index annotations for a given table. When you create multi-column indexes, you need to specify an order for the columns in the index. For example, the following code creates a multi-column index on Rating and BlogId called IX_BlogAndRating. BlogId is the first column in the index and Rating is the second.
public class Post
{
public int Id { get; set; }
public string Title { get; set; }
public string Content { get; set; }
[Index("IX_BlogIdAndRating", 2)]
public int Rating { get; set; }
[Index("IX_BlogIdAndRating", 1)]
public int BlogId { get; set; }
}
Please refer to this link for further information.
Comments
Use this to define it in config class, if you're avoiding using annotations:
public class YourTableConfig : EntityTypeConfiguration<YourTableEntity>
{
public YourTableConfig()
{
ToTable("YourTableDbName");
HasKey(u => u.Id);
Property(c => c.CompanyId).HasColumnType("nvarchar").HasMaxLength(9).IsRequired();
HasIndex(x => x.CompanyId).IsUnique(); // This sets the unique index
}
}
