GDAL c# API returned different WKT from gdalinfo

Question

I've found completely different results in WKT strings while using gdalinfo utility and method from c# API GetProjectionRef(). In the first case the result was:

PROJCS["WGS 84 / Pseudo-Mercator",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",0],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +
x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"],
    AUTHORITY["EPSG","3857"]]
Origin = (4042799.739385183900000,6382762.252179093700000)

but in the second one

LOCAL_CS[\"WGS 84 / Pseudo-Mercator\",
    GEOGCS[\"WGS 84\",
        DATUM[\"unknown\",
            SPHEROID[\"unretrievable - using WGS84\",6378137,298.257223563]],
        PRIMEM[\"Greenwich\",0],
        UNIT[\"degree\",0.0174532925199433]],
            AUTHORITY[\"EPSG\",\"3857\"],
        UNIT[\"metre\",1]]

So, the questions are 1) Why results are different? 2) How I can receive WKT with projected coordinate system from c# code as in the first case?