How to add description to columns in Entity Framework 4.3 code first using migrations?

Question

I\'m using Entity Framework 4.3.1 code first with explicit migrations. How do I add descriptions for columns either in the entity configuration classes or the migrations, so

Answer 1

thank you Mr.Mahmoodvcs for the great solution. allow me to modify it just replace "DisplayAttribute" with "DescriptionAttribute" insted of using :

[Display(Name="Description here")]

you will use :

[Description("Description here")]

so it includes the table as well.

    public class DbDescriptionUpdater
   where TContext : System.Data.Entity.DbContext
{
    public DbDescriptionUpdater(TContext context)
    {
        this.context = context;
    }

    Type contextType;
    TContext context;
    DbTransaction transaction;
    public void UpdateDatabaseDescriptions()
    {
        contextType = typeof(TContext);
        this.context = context;
        var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
        transaction = null;
        try
        {
            context.Database.Connection.Open();
            transaction = context.Database.Connection.BeginTransaction();
            foreach (var prop in props)
            {
                if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
                {
                    var tableType = prop.PropertyType.GetGenericArguments()[0];
                    SetTableDescriptions(tableType);
                }
            }
            transaction.Commit();
        }
        catch
        {
            if (transaction != null)
                transaction.Rollback();
            throw;
        }
        finally
        {
            if (context.Database.Connection.State == System.Data.ConnectionState.Open)
                context.Database.Connection.Close();
        }
    }

    private void SetTableDescriptions(Type tableType)
    {
        string fullTableName = context.GetTableName(tableType);
        Regex regex = new Regex(@"(\[\w+\]\.)?\[(?.*)\]");
        Match match = regex.Match(fullTableName);
        string tableName;
        if (match.Success)
            tableName = match.Groups["table"].Value;
        else
            tableName = fullTableName;

        var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
        if (tableAttrs.Length > 0)
            tableName = ((TableAttribute)tableAttrs[0]).Name;
        var table_attrs = tableType.GetCustomAttributes(typeof(DescriptionAttribute), false);
        if (table_attrs != null && table_attrs.Length > 0)
            SetTableDescription(tableName, ((DescriptionAttribute)table_attrs[0]).Description);
        foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
        {
            if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))
                continue;
            var attrs = prop.GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (attrs != null && attrs.Length > 0)
                SetColumnDescription(tableName, prop.Name, ((DescriptionAttribute)attrs[0]).Description);
        }
    }

    private void SetColumnDescription(string tableName, string columnName, string description)
    {

        string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
        var prevDesc = RunSqlScalar(strGetDesc);
        if (prevDesc == null)
        {
            RunSql(@"EXEC sp_addextendedproperty 
                @name = N'MS_Description', @value = @desc,
                @level0type = N'Schema', @level0name = 'dbo',
                @level1type = N'Table',  @level1name = @table,
                @level2type = N'Column', @level2name = @column;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@column", columnName),
                                                   new SqlParameter("@desc", description));
        }
        else
        {
            RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table,
                    @level2type = N'Column', @level2name = @column;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@column", columnName),
                                                   new SqlParameter("@desc", description));
        }
    }
    private void SetTableDescription(string tableName,  string description)
    {

        string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
        var prevDesc = RunSqlScalar(strGetDesc);
        if (prevDesc == null)
        {
            RunSql(@"EXEC sp_addextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@desc", description));
        }
        else
        {
            RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@desc", description));
        }
    }
    DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = context.Database.Connection.CreateCommand();
        cmd.CommandText = cmdText;
        cmd.Transaction = transaction;
        foreach (var p in parameters)
            cmd.Parameters.Add(p);
        return cmd;
    }
    void RunSql(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        cmd.ExecuteNonQuery();
    }
    object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        return cmd.ExecuteScalar();
    }

}
public static class ReflectionUtil
{

    public static bool InheritsOrImplements(this Type child, Type parent)
    {
        parent = ResolveGenericTypeDefinition(parent);

        var currentChild = child.IsGenericType
                               ? child.GetGenericTypeDefinition()
                               : child;

        while (currentChild != typeof(object))
        {
            if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
                return true;

            currentChild = currentChild.BaseType != null
                           && currentChild.BaseType.IsGenericType
                               ? currentChild.BaseType.GetGenericTypeDefinition()
                               : currentChild.BaseType;

            if (currentChild == null)
                return false;
        }
        return false;
    }

    private static bool HasAnyInterfaces(Type parent, Type child)
    {
        return child.GetInterfaces()
            .Any(childInterface =>
            {
                var currentInterface = childInterface.IsGenericType
                    ? childInterface.GetGenericTypeDefinition()
                    : childInterface;

                return currentInterface == parent;
            });
    }

    private static Type ResolveGenericTypeDefinition(Type parent)
    {
        var shouldUseGenericType = true;
        if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
            shouldUseGenericType = false;

        if (parent.IsGenericType && shouldUseGenericType)
            parent = parent.GetGenericTypeDefinition();
        return parent;
    }
}

public static class ContextExtensions
{
    public static string GetTableName(this DbContext context, Type tableType)
    {
        MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
                         .MakeGenericMethod(new Type[] { tableType });
        return (string)method.Invoke(context, new object[] { context });
    }
    public static string GetTableName(this DbContext context) where T : class
    {
        ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;

        return objectContext.GetTableName();
    }

    public static string GetTableName(this ObjectContext context) where T : class
    {
        string sql = context.CreateObjectSet().ToTraceString();
        Regex regex = new Regex("FROM (?.*) AS");
        Match match = regex.Match(sql);

        string table = match.Groups["table"].Value;
        return table;
    }
}

                                                        

              
                
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