c#

public static string MapSqlServerTypeToFluentMigrator(string sqlType)
{
    sqlType = sqlType.ToLowerInvariant();

    if (sqlType.StartsWith("varchar") || sqlType.StartsWith("nvarchar") || sqlType.StartsWith("char") || sqlType.StartsWith("nchar") || sqlType.StartsWith("text") || sqlType.StartsWith("ntext"))
        return "AsString()";
    if (sqlType.StartsWith("int"))
        return "AsInt32()";
    if (sqlType.StartsWith("bigint"))
        return "AsInt64()";
    if (sqlType.StartsWith("smallint"))
        return "AsInt16()";
    if (sqlType.StartsWith("tinyint"))
        return "AsByte()";
    if (sqlType.StartsWith("bit"))
        return "AsBoolean()";
    if (sqlType.StartsWith("decimal") || sqlType.StartsWith("numeric") || sqlType.StartsWith("money") || sqlType.StartsWith("smallmoney"))
        return "AsDecimal()";
    if (sqlType.StartsWith("float"))
        return "AsDouble()";
    if (sqlType.StartsWith("real"))
        return "AsSingle()";
    if (sqlType.StartsWith("datetime") || sqlType.StartsWith("smalldatetime") || sqlType.StartsWith("datetime2"))
        return "AsDateTime()";
    if (sqlType.StartsWith("date"))
        return "AsDate()";
    if (sqlType.StartsWith("time"))
        return "AsTime()";
    if (sqlType.StartsWith("uniqueidentifier"))
        return "AsGuid()";
    if (sqlType.StartsWith("binary") || sqlType.StartsWith("varbinary") || sqlType.StartsWith("image") || sqlType.StartsWith("rowversion") || sqlType.StartsWith("timestamp"))
        return "AsBinary()";

    return "AsCustom(\"" + sqlType + "\")"; // fallback
}