Improvements around DBNull.Value for DataRowExtensions (dotnet#9080)

Closes dotnet#9077

Author: roji

xml/System.Data/DataRowExtensions.xml

@@ -107,9 +107,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> does not support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> and <xref:System.Data.DataTable> do not support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is <xref:System.DBNull.Value> and `T` is a reference type or nullable type, the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is <xref:System.DBNull.Value?displayProperty=nameWithType> and `T` is a reference type or nullable type, the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -167,9 +167,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is **null** and `T` is a reference type or nullable type, then the return type will be **null**.  The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is **null** and `T` is a reference type or nullable type, then the return type will be **null**.  The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -227,9 +227,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class. A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> does not support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types. If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class. A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> and <xref:System.Data.DataTable> do not support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types. If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is **null** and `T` is a reference type or nullable type, the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is **null** and `T` is a reference type or nullable type, the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -289,9 +289,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -351,9 +351,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -413,9 +413,9 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value>, the returned nullable type will have a value of **null**.  
+ The <xref:System.Data.DataSet> class represents **null** values with the <xref:System.DBNull.Value> instance of the <xref:System.DBNull> class.  A Language-Integrated Query (LINQ) expression that accessed a column with a **null** value would generate a <xref:System.InvalidCastException> at run time. Additionally, <xref:System.Data.DataSet> doesn't support nullable types. The <xref:System.Data.DataRowExtensions.Field%2A> method provides support for accessing columns as nullable types.  If the underlying value in the <xref:System.Data.DataSet> is <xref:System.DBNull.Value?displayProperty=nameWithType>, the returned nullable type will have a value of **null**.  
   
- If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value>.  
+ If the value of the specified <xref:System.Data.DataColumn> is null and `T` is a reference type or nullable type, then the return type will be **null**. The <xref:System.Data.DataRowExtensions.Field%2A> method will not return <xref:System.DBNull.Value?displayProperty=nameWithType>.  
   
  The <xref:System.Data.DataRowExtensions.Field%2A> method does not perform type conversions. If type conversion is required, you should first obtain the column value by using the <xref:System.Data.DataRowExtensions.Field%2A> method. The column value should then be converted to another type.  
   
@@ -483,7 +483,7 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value> in the underlying <xref:System.Data.DataColumn>.  
+ If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value?displayProperty=nameWithType> in the underlying <xref:System.Data.DataColumn>.  
   
  The <xref:System.Data.DataRowExtensions.SetField%2A> method does not perform any type conversions. This does not mean, however, that a type conversion will not occur. The <xref:System.Data.DataRowExtensions.SetField%2A> method exposes the ADO.NET 2.0 behavior of the <xref:System.Data.DataRow> class. A type conversion could be performed by the <xref:System.Data.DataRow> object and the converted value would then be saved to the row.  
   
@@ -545,7 +545,7 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value> in the underlying <xref:System.Data.DataColumn>.  
+ If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value?displayProperty=nameWithType> in the underlying <xref:System.Data.DataColumn>.  
   
  The <xref:System.Data.DataRowExtensions.SetField%2A> method does not perform any type conversions. This does not mean, however, that a type conversion will not occur. The <xref:System.Data.DataRowExtensions.SetField%2A> method exposes the ADO.NET 2.0 behavior of the <xref:System.Data.DataRow> class. A type conversion could be performed by the <xref:System.Data.DataRow> object and the converted value would then be saved to the row.  
   
@@ -606,7 +606,7 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value> in the underlying <xref:System.Data.DataColumn>.  
+ If `value` is **null**, the <xref:System.Data.DataRowExtensions.SetField%2A> method converts the **null** value to <xref:System.DBNull.Value?displayProperty=nameWithType> in the underlying <xref:System.Data.DataColumn>.  
   
  The <xref:System.Data.DataRowExtensions.SetField%2A> method does not perform any type conversions. This does not mean, however, that a type conversion will not occur. The <xref:System.Data.DataRowExtensions.SetField%2A> method exposes the ADO.NET 2.0 behavior of the <xref:System.Data.DataRow> class. A type conversion could be performed by the <xref:System.Data.DataRow> object and the converted value would then be saved to the row.