Compare Two DataTables and copy Rows in Third DataTable with status using C# and VB.Net

Hi yogesjoshi,

Check this example. Now please take its reference and correct your code.

HTML

<table>
    <tr>
        <td>
            <asp:GridView ID="GridView1" runat="server" />
        </td>
        <td>
            <asp:GridView ID="GridView2" runat="server" />
        </td>
    </tr>
    <tr>
        <td colspan="2" align="center">
            <asp:GridView ID="GridView3" runat="server" />
        </td>
    </tr>
</table>

Namespaces 

C# 

using System.Data;

VB.Net 

Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    DataTable dt1 = new DataTable();
    dt1.Columns.Add("Department");
    dt1.Columns.Add("name");
    dt1.Columns.Add("marks");
    dt1.Rows.Add("it", "abc", 80);
    dt1.Rows.Add("cs", "xyz", 67);
    dt1.Rows.Add("mec", "abc", 76);
    dt1.Rows.Add("ece", "xyz", 73);

    DataTable dt2 = new DataTable();
    dt2.Columns.Add("Department");
    dt2.Columns.Add("name");
    dt2.Columns.Add("marks");
    dt2.Rows.Add("it", "abc", 80);
    dt2.Rows.Add("cs", "xyz", 50);
    dt2.Rows.Add("mec", "abc", 76);
    dt2.Rows.Add("eee", "abc", 40);

    DataTable dt3 = dt1.Clone();
    dt3.Columns.Add("status");

    for (int i = 0; i < dt1.Rows.Count; i++)
    {
        string department = dt1.Rows[i]["Department"].ToString();
        string name = dt1.Rows[i]["name"].ToString();
        string mark = dt1.Rows[i]["marks"].ToString();

        DataRow[] dr = dt2.Select("Department='" + department + "' AND name='" + name + "'");
        if (dr.Length > 0)
        {
            if (dr[0].ItemArray[2].ToString() == mark)
            {
                dt3.Rows.Add(department, name, mark, "same record");
            }
            else
            {
                dt3.Rows.Add(department, name, mark, "modified record");
            }
        }
        else
        {
            dt3.Rows.Add(department, name, mark, "deleted record");
        }
    }

    List<DataRow> rows = dt2.AsEnumerable()
                                .Where(x => !dt1.AsEnumerable()
                                                .Select(y => y.Field<string>("Department"))
                                                .Contains(x.Field<string>("Department"))).ToList();
    for (int i = 0; i < rows.Count; i++)
    {
        dt3.Rows.Add(rows[i].ItemArray[0], rows[i].ItemArray[1], rows[i].ItemArray[2], "new record");
    }

    GridView1.DataSource = dt1;
    GridView1.DataBind();
    GridView2.DataSource = dt2;
    GridView2.DataBind();
    GridView3.DataSource = dt3;
    GridView3.DataBind();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim dt1 As DataTable = New DataTable()
    dt1.Columns.Add("Department")
    dt1.Columns.Add("name")
    dt1.Columns.Add("marks")
    dt1.Rows.Add("it", "abc", 80)
    dt1.Rows.Add("cs", "xyz", 67)
    dt1.Rows.Add("mec", "abc", 76)
    dt1.Rows.Add("ece", "xyz", 73)

    Dim dt2 As DataTable = New DataTable()
    dt2.Columns.Add("Department")
    dt2.Columns.Add("name")
    dt2.Columns.Add("marks")
    dt2.Rows.Add("it", "abc", 80)
    dt2.Rows.Add("cs", "xyz", 50)
    dt2.Rows.Add("mec", "abc", 76)
    dt2.Rows.Add("eee", "abc", 40)

    Dim dt3 As DataTable = dt1.Clone()
    dt3.Columns.Add("status")

    For i As Integer = 0 To dt1.Rows.Count - 1
        Dim department As String = dt1.Rows(i)("Department").ToString()
        Dim name As String = dt1.Rows(i)("name").ToString()
        Dim mark As String = dt1.Rows(i)("marks").ToString()

        Dim dr As DataRow() = dt2.[Select]("Department='" & department & "' AND name='" & name & "'")
        If dr.Length > 0 Then
            If dr(0).ItemArray(2).ToString() = mark Then
                dt3.Rows.Add(department, name, mark, "same record")
            Else
                dt3.Rows.Add(department, name, mark, "modified record")
            End If
        Else
            dt3.Rows.Add(department, name, mark, "deleted record")
        End If
    Next

    Dim rows As List(Of DataRow) = dt2.AsEnumerable().Where(Function(x) Not dt1.AsEnumerable().[Select](Function(y) y.Field(Of String)("Department")).Contains(x.Field(Of String)("Department"))).ToList()
    For i As Integer = 0 To rows.Count - 1
        dt3.Rows.Add(rows(i).ItemArray(0), rows(i).ItemArray(1), rows(i).ItemArray(2), "new record")
    Next

    GridView1.DataSource = dt1
    GridView1.DataBind()
    GridView2.DataSource = dt2
    GridView2.DataBind()
    GridView3.DataSource = dt3
    GridView3.DataBind()
End Sub

Screenshot