There are two Entity Framework methods to influence the resulting Oracle Data Type: Data Annotations and the Code First Fluent API. As illustrated with the String type, you can influence the resulting Oracle Data Type for a property as well as characteristics of that data type. The type mappings listed in the previous table represent the mappings that occur by default or what is known as convention in Entity Framework. Influencing the Oracle Data Type Characteristics If the character data can be longer than 4000 bytes, it may be more appropriate to use CLOB or NCLOB column. As such, these columns may not be able to store 4000 characters even if Max Length is set to 4000 characters since one character may require multiple number of bytes of storage, depending on the data and the database character set. However, due to the Oracle database limit, these columns can store only up to 4000 bytes. The character based columns, namely, CHAR, NCHAR, VARCHAR2, NVARCHAR2 will be created using character semantics to be able to store the specified Max Length amount of characters. Set Column Type to UROWID using HasColumnType() fluent API or Column data annotation Set Column Type to ROWID using HasColumnType() fluent API or Column data annotation Note: The long data type is deprecated and not recommended. Set Column Type to LONG using HasColumnType() fluent API or Column data annotation Set Max Length to <= 2000 using HasMaxLength() fluent API or MaxLength annotation and Set Column Type to CHAR using HasColumnType() fluent API or Column data annotation Set Max Length to <= 1000 using HasMaxLength() fluent API or MaxLength annotation and Set Column Type to NCHAR using HasColumnType() fluent API or Column data annotation Set Max Length to <= 4000 using HasMaxLength() fluent API or MaxLength data annotation and set Unicode to false using IsUnicode() fluent API Set Max Length to <= 2000 using HasMaxLength() fluent API or MaxLength data annotation Set Unicode to false using IsUnicode() fluent API Reference the EDM Mapping sections in the documentation for additional information. Note: The default mapping of integer types may be specified in the EDM Mapping configuration. But it's not always the case that the names of the classes match the names of the tables in your database.Note: Requires use of EDM Mapping configuration. You can use Code First with an existing database. If you are letting Code First create the database, and also want to change the name of the tables it is creating. Tableĭefault Code First convention creates a table name similar to the class name. If the user sets the Title which contains more than 24 characters, then EF will throw EntityValidationError. Public DateTime EnrollmentDate Įntity Framework also validates the value of a property for StringLength attribute. So to handle this, a Key attribute is added which will make it a primary key. Let’s take a look at the following code of a Student class which contains StdntID, but it doesn’t follow the default Code First convention. You can use the key annotation to specify which property is to be used as the EntityKey. When Code First does not find a property that matches this convention, it will throw an exception because of Entity Framework’s requirement that you must have a key property. Now let’s suppose Student class used the name StdntID instead of ID. The Student, Course and Enrollment classes follow this convention. The property will map to a primary key column in the database. One of the conventions that Code First depends on is how it implies which property is the key in each of the Code First classes.Ĭonvention is to look for a property named “Id” or one that combines the class name and “Id”, such as “StudentId”. namespace includes the following attributes that impacts the schema of the database.Įntity Framework relies on every entity having a key value that it uses for tracking entities. includes the following attributes that impacts the nullability or size of the column. DataAnnotation attributes override default CodeFirst conventions. NET applications, such as ASP.NET MVC which allows these applications to leverage the same annotations for client-side validations. DataAnnotations are also understood by a number of. DataAnnotations is used to configure the classes which will highlight the most commonly needed configurations.
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