C# - While Storing 0.0 In A Datatable It Gets Stored As 0 Only?

I have a datatable dt1 which has 3 columns a,b,c( of datatype string , float ,float resp). Then I've a datatable dt2 which is clone of dt1 , and the values of dt1 is merged into dt2.

Now the issue is for a particular condition :

when the first row is this

dt1.Rows.Add("xyz", 0.0, 0.0);

But I can see the value is taken as xyz,0,0 in the datatable. This i am merging to dt2 as

if (dt2 == null)
{
dt2 = dt1.Clone();
}
dt2.Merge(dt1, true);

Now when I merge for the second time with say some vale in dt1 as ("mnp",4.5,8.9) i get an error at dt2.Merge(dt1, true);

Error: .b and .b have conflicting properties: DataType property mismatch.

where b is the column name.

Have defined the table dt1 as :

DataTable dt1 = new DataTable();
dt1.Columns.Add("a", typeof(string));
dt1.Columns.Add("b", typeof(float));
dt1.Columns.Add("c", typeof(float));`