How to change the schema at runtime in Dapper-Extensions?

Question

I am using Dapper Extensions but I have multiple schema names in My DB.

I found the an answer in below link but it assumes that I have only one schema name and this is not my case. Dapper Extensions Change Schema

What is the right way to change the schema name at the runtime?

I might have found a solution to this issue :) – Kamil Budziewski Apr 23 '18 at 09:01 — Kamil Budziewski, Apr 23 '18 at 09:01

score 0 · Answer 1 · answered Apr 23 '18 at 09:00

Probably you won't use it anymore, but maybe there are more guys up there trying to figure it out.

I've been checking out how dapper works when running GetAll<> and Insert<>.

What it does:

var type = typeof(T);
var cacheType = typeof(List<T>);

if (!GetQueries.TryGetValue(cacheType.TypeHandle, out string sql))
{
    GetSingleKey<T>(nameof(GetAll));
    var name = GetTableName(type); <--- key thing

    sql = "select * from " + name;
    GetQueries[cacheType.TypeHandle] = sql;
}

So I've checked what GetTableName was doing:

private static string GetTableName(Type type)
{
    if (TypeTableName.TryGetValue(type.TypeHandle, out string name)) return name;

    if (TableNameMapper != null)
    {
        name = TableNameMapper(type); <-- key thing
    }
    else
    {
        //NOTE: This as dynamic trick should be able to handle both our own Table-attribute as well as the one in EntityFramework 
        var tableAttr = type
#if NETSTANDARD1_3
            .GetTypeInfo()
#endif
            .GetCustomAttributes(false).SingleOrDefault(attr => attr.GetType().Name == "TableAttribute") as dynamic;
        if (tableAttr != null)
        {
            name = tableAttr.Name;
        }
        else
        {
            name = type.Name + "s";
            if (type.IsInterface() && name.StartsWith("I"))
                name = name.Substring(1);
        }
    }

    TypeTableName[type.TypeHandle] = name;
    return name;
}

Solution:

So I thought I can implement my own table name mapper with code like this:

SqlMapperExtensions.TableNameMapper = DapperMapper.TableNameMapper();

And

public static SqlMapperExtensions.TableNameMapperDelegate TableNameMapper()
{
    return (type) =>
    {
        var has = Attribute.GetCustomAttribute(type, typeof(CastleTableAttribute));
        if (has != null)
        {
            return $"{ConfigurationProvider.Schema}.{type.Name}";
        }
        else
        {
            return type.Name;
        }
    };
}

With that name mapper you just need to mark your table with that.

[CastleTable]
class CubeTimestamps
{
    [ExplicitKey]
    public int cube_id { get; set; }
    public DateTime cube_timestamp { get; set; }
}

you can implement your name mapper to use [TableName] attribute also. Because my simple implementation hides this feature.

Enjoy :)

@BernardVanderBeken it's my configurationPovider it returns string from App.Config — Kamil Budziewski, Oct 10 '19 at 12:19

How to change the schema at runtime in Dapper-Extensions?

1 Answers1