How to get the exact type of numeric columns incl. scale and precision?

问题

Is there a way to know the exact type of a column in a DataTable? Right now I am doing this:

DataTable st = dataReader.GetSchemaTable();
foreach (DataColumn col in st.Columns)
{
   var type = col.DataType;
}

Now with type.Name I am able to find if it is a number(int or decimal..) or string but the problem is that I need the exact type, for example if in database let say column Rate is NUMBER(4,3) then here in my code I am only getting type as 'Decimal' and no information about the Format 4,3.

Now the requirement is I need to format the values as per their type for eg. if Rate=1.4 it should be shown as 0001.400 (according to the Format NUMBER(4,3)). Hence here since I do not have info I am not able to process the values further. Is there anyway to know the same?

Thanks

回答1:

You can use NumericPrecision and NumericScale:

using (var con = new SqlConnection(Properties.Settings.Default.RM2ConnectionString))
using (var cmd = new SqlCommand("SELECT * FROM dbo.Test", con))
{
    con.Open();
    using (var reader = cmd.ExecuteReader())
    using (var schemaTable = reader.GetSchemaTable())
    {
        foreach (DataRow row in schemaTable.Rows)
        {
            string column = row.Field<string>("ColumnName");
            string type = row.Field<string>("DataTypeName");
            short precision = row.Field<short>("NumericPrecision");
            short scale = row.Field<short>("NumericScale");
            Console.WriteLine("Column: {0} Type: {1} Precision: {2} Scale: {3}", column, type, precision, scale);
        }
    }
}

More informations: GetSchemaTable

I have tested it with a fresh table with a single column NumberColumn of type numeric(4, 3):

Column: NumberColumn Type: decimal Precision: 4 Scale: 3

回答2:

The DataTable returned by dataReader.GetSchemaTable() is the schema of the underlying result. This table contains, those many records as many columns in the underlying table. So you need to loop through the rows. Each row contains the metadata of the single column of the underlying table. You can get the metadata of the column as below

DataTable st = reader.GetSchemaTable();
                    foreach (DataRow row in st.Rows)
                    {
                        Console.Write(string.Format("ColumnName:{0} DataType:{1} Ordinal:{2} Precision:{3} Size:{4} Scale:{5}", 
                            row["ColumnName"], row["DataTypeName"], row["ColumnOrdinal"], 
                            row["NumericPrecision"], row["ColumnSize"], row["NumericScale"]));
                    }

来源：https://stackoverflow.com/questions/24164439/how-to-get-the-exact-type-of-numeric-columns-incl-scale-and-precision

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