There are two ways to achieve this:
1. You can iterate the DataTable object and check the value of each column using below code:
foreach (DataRow row in dt.AsEnumerable())
{
foreach (DataColumn col in dt.Columns)
{
if (row.IsNull(col))
{
if (row[col].GetType().Equals(typeof(int)))
row[col] = 0;
else if(row[col].GetType().Equals(typeof(string)))
row[col] = "No Data";
}
}
}
2. In the sql query we can check this :
ISNULL(col,0)
ISNULL(col, '')
Thanks