Datatable.select() not consistent

i have a dataset
name Asset_ID
abc     48
xyz      49
tuy      50
.
.
.
jkl      60
.
.
mkl    78

datarow[] dr = dsetCurrentGrid.Tables[0].Select("Assets_ID=48");
wont return any row...but
datarow[] dr = dsetCurrentGrid.Tables[0].Select("Assets_ID=60");
returns row.
What might be the reason?

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