How to get the primarykey name of the table in EntityFramework C#?

 Here is how to get the primary key of an entitySetName
var primaryKeyName = objDb
   .MetadataWorkspace
   .GetEntityContainer(objDb.DefaultContainerName, System.Data.Metadata.Edm.DataSpace.CSpace)
   .BaseEntitySets
   .First(meta => meta.ElementType.Name == entitySetName)
   .ElementType
   .KeyMembers
   .Select(k => k.Name)
   .FirstOrDefault();

How to check the Key exists or not in EntityFramework C#?

This method will help to get the key exists or not from an entityset in EntityFramework
Here
TargetTable is the Enum where I have all the tables names
string keyValue is the value for which i am checking exists or not

 public bool CheckKey(TargetTable tableName, string keyValue, MyMotorEntities objDb)
{
bool isKeyAlreadyExists = false;
try
                            {
                                string entitySetName = Enum.GetName(typeof(TargetTable), tableName);
                                var primaryKeyName = objDb
   .MetadataWorkspace
   .GetEntityContainer(objDb.DefaultContainerName, System.Data.Metadata.Edm.DataSpace.CSpace)
   .BaseEntitySets
   .First(meta => meta.ElementType.Name == entitySetName)
   .ElementType
   .KeyMembers
   .Select(k => k.Name)
   .FirstOrDefault();
                                List<KeyValuePair<string, object>> lstEnum = new List<KeyValuePair<string, object>>();
                                lstEnum.Add(new KeyValuePair<string, object>(primaryKeyName, keyValue));
                                var lsttype = from t in lstEnum select t;
                                IEnumerable<KeyValuePair<string, object>> IeList = ((IEnumerable<KeyValuePair<string, object>>)lsttype).Select(x => x).AsQueryable();
                                System.Data.EntityKey key = new System.Data.EntityKey("MyMotorEntities." + entitySetName , IeList);
                                var tbl = objDb.GetObjectByKey(key);
if (tbl!=null)
                {
                    isKeyAlreadyExists = true;
                }
                            }
                            catch (Exception ex)
                            {

                            }
 return isKeyAlreadyExists;
}

How to update a record through EntityFramework in C#?

To update record with the help of EF we use this code
public void Update(tblAdmin objtblAdmin)
{
try
{
using (MyMotorEntities objDb = new MyMotorEntities())
{
var objAdmin = (from t in objDb.tblAdmins.Where(p => p.IdAdmins == objtblAdmin.IdAdmins) select t).FirstOrDefault();
if (objAdmin.IdAdmins > 0)
{objAdmin.Email = objtblAdmin.Email;
objAdmin.Firstname = objtblAdmin.Firstname;
objDb.SaveChanges();
}

}
ReportSuccess();

}
catch (Exception ex)
{
ReportError(ex);
}
}

But what happens when the tblAdmin has lots of fields :) ok don't worry we can use Attach for this.Attach allows us to attach to a record within the context, perform a straight replace on the record with the new modified record and save back the changes and All just within just 3 lines of codes... lolz :)

Here is this ...

public void Update(tblAdmin objtblAdmin)
{
try
{

using (MyMotorEntities objDb = new MyMotorEntities())
{
objDb.tblAdmins.Attach(objDb.tblAdmins.Single(c => c.IdAdmins == objtblAdmin.IdAdmins));
objDb.tblAdmins.ApplyCurrentValues(objtblAdmin);
objDb.SaveChanges();
}

ReportSuccess();
}
catch (Exception ex)
{
ReportError(ex);
}
}

Cheers :)