private static T FieldValue <T>(this DataRow dataRow, DataColumn column)
{
if (dataRow == null)
{
throw new ArgumentNullException("dataRow");
}
if (column == null)
{
throw new ArgumentNullException("column");
}
try
{
return(DbValueConverter.ConvertFrom <T>(dataRow[column]));
}
catch (Exception e)
{
e.Data.Add("DataColumnName", column.ColumnName);
throw;
}
}
/// <summary>
/// 异步执行查询并返回首行首列
/// </summary>
/// <typeparam name="T">返回值类型</typeparam>
/// <param name="query">要执行的查询对象</param>
/// <param name="token">取消指示</param>
/// <returns>查询结果</returns>
public async static Task <T> ExecuteScalarAsync <T>(this IAsyncDbExecutableQuery query, CancellationToken token = default(CancellationToken))
{
return(DbValueConverter.ConvertFrom <T>(await ExecuteScalarAsync(query, token)));
}
/// <summary>
/// 执行查询并返回首行首列
/// </summary>
/// <typeparam name="T">返回值类型</typeparam>
/// <param name="query">要执行的查询对象</param>
/// <returns>查询结果</returns>
public static T ExecuteScalar <T>(this IDbExecutableQuery query)
{
return(DbValueConverter.ConvertFrom <T>(ExecuteScalar(query)));
}