Expression.Field Method (Expression, String)

Parameters

• expression
  Type: System.Linq.Expressions.Expression
  An Expression whose Type contains a field named fieldName. This can be null for static fields.

• fieldName
  Type: System.String
  The name of a field to be accessed.

Return Value

Type: System.Linq.Expressions.MemberExpression
A MemberExpression that has the NodeType property equal to MemberAccess, the Expression property set to expression, and the Member property set to the FieldInfo that represents the field denoted by fieldName.

' Add the following directive to your file:
' Imports System.Linq.Expressions

Class TestFieldClass
    Dim sample As Integer = 40
End Class

Sub TestField()

    Dim obj As New TestFieldClass()

    ' This expression represents accessing a field.
    ' For static fields, the first parameter must be Nothing.
    Dim fieldExpr As Expression = Expression.Field(
          Expression.Constant(obj),
          "sample"
      )

    ' The following statement first creates an expression tree,
    ' then compiles it, and then runs it.
    outputBlock.Text &= Expression.Lambda(Of Func(Of Integer))(fieldExpr).Compile()() & vbCrLf
End Sub

' This code example produces the following output:
'
' 40

// Add the following directive to your file:
// using System.Linq.Expressions;  

class TestFieldClass
{
   int sample = 40;
}

static void TestField(System.Windows.Controls.TextBlock outputBlock)
{
   TestFieldClass obj = new TestFieldClass();

   // This expression represents accessing a field.
   // For static fields, the first parameter must be null.
   Expression fieldExpr = Expression.Field(
       Expression.Constant(obj),
       "sample"
   );

   // The following statement first creates an expression tree,
   // then compiles it, and then runs it.
   outputBlock.Text += Expression.Lambda<Func<int>>(fieldExpr).Compile()() + "\n";
}

// This code example produces the following output:
//
// 40