Question

hey guys, i’m finding little difficult to prepare a where clause in following update method
i’m creating a update method, here am i doin’ this in a rightway ? but still m confused that how do i know that which property is to use in where clause

or any better approach to create a generic update method ? i wud be very thankfull

EDIT

    public bool UpdateData(object Entity, ref String error)
    {
        Type objectType = Entity.GetType();
        PropertyInfo[] properties = objectType.GetProperties();
        error = "";
        string column = null;
        int i = 0;
        SqlConnection conn = OpenConnection();
        SqlCommand sqlcommand=null;
        foreach (PropertyInfo info in properties)
        {
            if (i == 0)
            {
                i++;
                continue;

            }
            column += (i >= 0 && i < properties.Length - 1) ? string.Format(@"{0}=@{0},", info.Name) : string.Format(@"{0}=@{0}",info.Name);
            i++;
        }
        try
        {
            string sqlQuery = string.Format(@"update {0} set {1} 
            where {2}='{3}'", objectType.Name, column,1,1);//see here m not getting how to prepare this where clause
            sqlcommand = new SqlCommand(sqlQuery, conn);
            i = 0;
            foreach (PropertyInfo info in properties)
            {
                if (i == 0)
                {
                    i++;
                    continue;

                }
                sqlcommand.Parameters.AddWithValue(string.Format("@{0}", info.Name), info.GetValue(Entity, null));
            }
            sqlcommand.ExecuteNonQuery();
            sqlcommand = null;
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
        finally
        {
            CloseConnection(conn);
        }
    }

EDIT

see in above code there is an if condition if (i == 0) in foreach loop i dont want to do this way coz here i’m assuming my objects property i.e employee_id is at 1st index in array of PropertyInfo[].. what if some one makes a class properties like public string employee_name{get,set} public string employee_add{get,set} public string employee_id{get,set} in this case the foreach loop will skip employee_name instead of ’employee_id’ coz i used if(i=0), i want a way to skip only identity value i.e employee_id in foreach loop in my update function irresptive of its index in propertyInfo array….. did i explained well ?

Answer 1

You can use a custom attribute or an interface to determine the property that represent the id of your entity and use it in your where clause. Although this approach has a negative side that you have to change your entity classes (which is not always possible).
Here’s an example :

[PrimaryKey]
public string EmployeeId
{
get;set;
}

or

public class Employee:IEntity
{
public object EntityId
{
get
{
return this.EmployeeId
}
}
}

another way might be to store the entities metadata somewhere else (a xml file or a dictionary for example)

for example:

<entities>
<entity type="Employee" primarykey="EmployeeId" />
</entities>

or

Hashtable EntityPrimaryKeys=new Hashtable{(typeof(Employee),"EmployeeId")};