Generic methods to read value from DataReader
Reading a value from DataReader is one of the most often and repetitive task for programmers working on database project. Here are the generic methods to make this work easy:
Method static T GetData<T> gets value from the specified DataReader for the specified Column name with the option to return default value or throw exception in case of DBNull.
1: private static T GetData<T>(IDataReader reader, string columnName, T valueInCaseOfDBNull, bool throwExpIfDBNull)
2: {
3: string errMsg = "Error from DataReaderHelper.GetData, Column Type : " + typeof(T).ToString() + " Additional Info : {0}.";
4: try
5: {
6: if (reader != null && !string.IsNullOrEmpty(columnName))
7: {
8: int columnIndex = reader.GetOrdinal(columnName);
9: T retValue;
10: if (!reader.IsDBNull(columnIndex))
11: {
12: retValue = (T)reader.GetValue(columnIndex);
13:
14: }
15: else
16: {
17: if (throwExpIfDBNull)
18: {
19: throw new DataException(string.Format(errMsg, "DBNull found while reading " + columnName));
20: }
21: else
22: {
23: retValue = valueInCaseOfDBNull;
24: }
25: }
26: return retValue;
27: }
28: else
29: {
30: throw new DataException(string.Format(errMsg, "DataReader object is null or ColumnName is null or empty"));
31: }
32: }
33: catch (Exception ex)
34: {
35: throw new DataException(string.Format(errMsg, "Error while reading column " + columnName), ex);
36: }
37:
38: }
And below are the three friendly public overloads to access above GetData method:
1: /// <summary>
2: /// Gets value from the specified DataReader for the specified Column name and
3: /// throws exception if corresponding field name contains DBNull
4: /// </summary>
5: public static T GetData<T>(IDataReader dr, string columnName)
6: {
7: return GetData<T>(dr, columnName, default(T), true);
8: }
9:
10: /// <summary>
11: /// Gets value from the specified DataReader for the specified Column name with
12: /// the option to throw exception or retun default value in case of DBNull
13: /// </summary>
14: public static T GetData<T>(IDataReader dr, string columnName, bool throwExpIfDBNull)
15: {
16: return GetData<T>(dr, columnName, default(T), throwExpIfDBNull);
17: }
18:
19: /// <summary>
20: /// Gets value from the specified DataReader for the specified Column name and
21: /// retuns specified default value in case of DBNull
22: /// </summary>
23: public static T GetData<T>(IDataReader dr, string columnName, T valueInCaseOfDBNull)
24: {
25: return (T)GetData(dr, columnName, valueInCaseOfDBNull, false);
26: }