How to modify one column of a table which is used as composite key

Hello Pakeeza,

Sorry to hear that :(

Here are a few things you can check and try:

1. Ensure the Key Attributes are Correct: Make sure that the ID, Student_branch, and School_branch attributes in your Entity class match the actual key attributes in your database. Verify that they are marked as [Key] in the class definition.

public class YourEntityClass
{
    [Key, Column(Order = 0)]
    public int ID { get; set; }

    [Key, Column(Order = 1)]
    public string Student_branch { get; set; }

    [Key, Column(Order = 2)]
    public string School_branch { get; set; }

    // other properties...
}

2. Ensure No Additional Constraints: Check if there are any database triggers, constraints, or other rules that might be preventing the update.

3. Try Loading and Updating Without Querying First: Instead of querying and then modifying, try creating a new instance of your entity, setting the necessary properties, and then updating it:

var student = new YourEntityClass
{
    ID = student_ID,
    Student_branch = "YourStudentBranch",
    School_branch = "ABC"
};

db.Entry(student).State = EntityState.Modified;
db.SaveChanges();

4. Check Database Logs: If possible, check the database logs or exceptions to get more specific information about why the update is failing.

If the issue persists after checking these points, there might be some specific details about your database model or configuration that require a closer look. If you can provide more details or code snippets related to your database model and entity class, I might be able to provide more targeted assistance.

Hi Prasad what you sid I am exactly doing the same but the column I am going to update is a part of primary key so getting exception "The property 'MyColumntobeupdated' is part of the object's key information and cannot be modified. " 

I also try to update all three columns whichmakes the primary key but same error 

When you define a composite primary key using multiple columns (in your case, ID, Student_branch, School_branch), Entity Framework treats those columns as a single unit, and you cannot modify individual columns of a primary key directly.

If you need to update the School_branch value for a specific row, you should update the entire entity instead of just modifying the School_branch property. Here is an example of how you can achieve this:

// Assuming you have a Student entity with the properties ID, Student_branch, and School_branch
var student = db.YourTableName
                 .Where(s => s.ID == student_ID && s.Student_branch == "YourStudentBranch")
                 .FirstOrDefault();

if (student != null)
{
    // Update the School_branch property
    student.School_branch = "ABC";

    // Mark the entire entity as modified
    db.Entry(student).State = System.Data.Entity.EntityState.Modified;

    // Save changes
    db.SaveChanges();
}

Replace YourTableName with the actual name of your table and adjust the condition in the Where clause based on your requirements.

By updating the entire entity and marking it as modified, Entity Framework will handle updating all the properties, including those that are part of the composite primary key.

I think you must delete the record then add it again using the new data. I am not an expert but probably you can make a transaction that does all that and then data would not be lost if there is an error.