DataRowExtensions.cs

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using System.Reflection;
 
namespace System.Data;
 
public static class DataRowExtensions
{
    private static class UnboxT<T>
    {
        internal static readonly Converter<object, T> s_unbox = Create();
 
        private static Converter<object, T> Create()
        {
            if (typeof(T).IsValueType)
            {
                if (!typeof(T).IsGenericType || !(typeof(T).GetGenericTypeDefinition() == typeof(Nullable<>)))
                {
                    return ValueField;
                }
                return (Converter<object, T>)Delegate.CreateDelegate(typeof(Converter<object, T>), typeof(UnboxT<T>).GetMethod("NullableField", BindingFlags.Static | BindingFlags.NonPublic).MakeGenericMethod(typeof(T).GetGenericArguments()[0]));
            }
            return ReferenceField;
        }
 
        private static T ReferenceField(object value)
        {
            if (value != DBNull.Value)
            {
                return (T)value;
            }
            return default(T);
        }
 
        private static T ValueField(object value)
        {
            if (value != DBNull.Value)
            {
                return (T)value;
            }
            throw DataSetUtil.InvalidCast(System.SR.Format(System.SR.DataSetLinq_NonNullableCast, typeof(T)));
        }
 
        private static TElem? NullableField<TElem>(object value) where TElem : struct
        {
            if (value != DBNull.Value)
            {
                return (TElem)value;
            }
            return null;
        }
    }
 
    public static T? Field<T>(this DataRow row, string columnName)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[columnName]);
    }
 
    public static T? Field<T>(this DataRow row, DataColumn column)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[column]);
    }
 
    public static T? Field<T>(this DataRow row, int columnIndex)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[columnIndex]);
    }
 
    public static T? Field<T>(this DataRow row, int columnIndex, DataRowVersion version)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[columnIndex, version]);
    }
 
    public static T? Field<T>(this DataRow row, string columnName, DataRowVersion version)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[columnName, version]);
    }
 
    public static T? Field<T>(this DataRow row, DataColumn column, DataRowVersion version)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        return UnboxT<T>.s_unbox(row[column, version]);
    }
 
    public static void SetField<T>(this DataRow row, int columnIndex, T? value)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        row[columnIndex] = ((object)value) ?? DBNull.Value;
    }
 
    public static void SetField<T>(this DataRow row, string columnName, T? value)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        row[columnName] = ((object)value) ?? DBNull.Value;
    }
 
    public static void SetField<T>(this DataRow row, DataColumn column, T? value)
    {
        DataSetUtil.CheckArgumentNull(row, "row");
        row[column] = ((object)value) ?? DBNull.Value;
    }
}