in c# I would like to compare datatables

I would like to compare two DataTables. A开发者_高级运维ll I need to know is are the contents different yes or no. Can any one recommend a quick way to compare them?

I would like to know if the contents (data) are diffrent

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I thought I had this problem down with code I had done recently and found what I was doing wasn't really working. So I had to revisit this and came across this post recently.

The way I was doing it before was by using WriteXml on both to memorystreams and running through the two strings 256 characters at a time looking for differences. While that worked a good portion of the time, I started to realize that my rows and columns weren't necessarily in the same order as the other despite being called from the same procedure.

So I reworked it by comparing hashcodes from each row. This allowed me in the end to compare all the content despite the columns and rows being in different order.

First I try to do some quick tests for differences like # of rows and columns and then by making sure the columns in the first table exist in the second. If we got that far, then it's time for the extensive testing w/ the hashcodes. I thought it might take a long time to run but turns out it's not as bad as I thought.

I know the code is in Visual Basic, I'm sorry about that as I saw you were looking for C#, but I'm sure it's easy to transition it over.

While this thread is old, I hope this code helps anyone looking to do the same thing. It sure beats checking cell by cell.

''' <summary>
''' Compares the data between both datatables to check if they have the same content or not.
''' Columns and Rows do not need to be in the same order as the other, just that the data in any of them need to be the same.
''' </summary>
''' <param name="dtbl_a">The first datatable to compare.</param>
''' <param name="dtbl_b">The second datatable to compare.</param>
''' <param name="debug">For troubleshooting and checking the function is working correctly.  Typically this is 'false'.</param>
''' <returns>Boolean:  False if the data between the two datatables are different, True if the data between them are the same.</returns>
''' <remarks></remarks>
Public Function dataTablesAreEqual _
                                  (ByRef dtbl_a As System.Data.DataTable, _
                                   ByRef dtbl_b As System.Data.DataTable, _
                                   ByVal debug As System.Boolean) As System.Boolean

    Dim recordCount(1) As System.Int32
    Dim columnCount(1) As System.Int32
    Dim length(1) As System.Int32
    Dim dtbl_check(1) As System.Data.DataTable
    Dim debugMessage As New System.Text.StringBuilder
    Dim errorMessage As System.String
    Dim result As System.Boolean

    Try
        If debug = True Then
            debugMessage.AppendLine("checking:  priliminary (and easy to see) tests being done...")
            debugMessage.AppendLine("checking:  what is nothing and what is not nothing.")

        End If

        If dtbl_a Is Nothing And dtbl_b Is Nothing Then
            result = True

            If debug = True Then
                debugMessage.AppendLine("decision:  " & result.ToString & "!")
                debugMessage.AppendLine("  reason:  dtbl_a Is Nothing And dtbl_b Is Nothing.")

            End If

            Return result

        ElseIf dtbl_a Is Nothing And dtbl_b IsNot Nothing Then
            result = False

            If debug = True Then
                debugMessage.AppendLine("decision:  " & result.ToString & "!")
                debugMessage.AppendLine("  reason:  dtbl_a Is Nothing And dtbl_b IsNot Nothing.")

            End If

            Return result

        ElseIf dtbl_a IsNot Nothing And dtbl_b Is Nothing Then
            result = False

            If debug = True Then
                debugMessage.AppendLine("decision:  " & result.ToString & "!")
                debugMessage.AppendLine("  reason:  dtbl_a IsNot Nothing And dtbl_b Is Nothing.")

            End If

            Return result

        End If

        If debug = True Then
            debugMessage.AppendLine("checking:  differences in row and column counts.")

        End If

        recordCount(0) = dtbl_a.Rows.Count
        columnCount(0) = dtbl_a.Columns.Count

        recordCount(1) = dtbl_b.Rows.Count
        columnCount(1) = dtbl_b.Columns.Count

        If recordCount(0) <> recordCount(1) Then
            result = False

            If debug = True Then
                debugMessage.AppendLine("decision:  " & result.ToString & "!")
                debugMessage.AppendLine("  reason:  the # of rows are different.")
                debugMessage.AppendLine("  reason:  dtbl_a has " & recordCount(0) & " record(s) and dtbl_b has " & recordCount(1) & " record(s).")

            End If

            Return result

        ElseIf columnCount(0) <> columnCount(1) Then
            result = False

            If debug = True Then
                debugMessage.AppendLine("decision:  " & result.ToString & "!")
                debugMessage.AppendLine("  reason:  the # of columns are different.")
                debugMessage.AppendLine("  reason:  dtbl_a has " & columnCount(0) & " column(s) and dtbl_b has " & columnCount(1) & " column(s).")

            End If

            Return result

        End If

        Dim lowerBound_Records As System.Int32
        Dim upperBound_Records As System.Int32
        Dim current_Record As System.Int32
        Dim lowerBound_Columns As System.Int32
        Dim upperBound_Columns As System.Int32
        Dim current_Column As System.Int32

        lowerBound_Records = 0
        upperBound_Records = (recordCount(0) - 1)
        lowerBound_Columns = 0
        upperBound_Columns = (columnCount(0) - 1)

        If debug = True Then
            debugMessage.AppendLine("checking:  columns exist in both tables (can be in different order).")

        End If

        For current_Column = lowerBound_Columns To upperBound_Columns
            Dim columnName As System.String
            Dim exists As System.Boolean

            columnName = dtbl_a.Columns(current_Column).ColumnName
            exists = dtbl_b.Columns.Contains(columnName)

            If exists = False Then
                result = False

                If debug = True Then
                    debugMessage.AppendLine("decision:  " & result.ToString & "!")
                    debugMessage.AppendLine("  reason:  the column [" & columnName & "] in dtbl_a does NOT EXIST in dtbl_b.")

                End If

                Return result

            End If

        Next current_Column

        dtbl_check(0) = New System.Data.DataTable
        dtbl_check(0).Columns.Add("index", GetType(System.Int32))
        dtbl_check(0).Columns.Add("hashCode", GetType(System.Int32))
        dtbl_check(0).Columns.Add("checked", GetType(System.DateTime))

        If debug = True Then
            dtbl_check(0).Columns.Add("dataRow", GetType(System.String))

        End If

        dtbl_check(0).PrimaryKey = New System.Data.DataColumn() {dtbl_check(0).Columns("index"), dtbl_check(0).Columns("hashCode")}
        dtbl_check(1) = dtbl_check(0).Copy

        If debug = True Then
            debugMessage.AppendLine("checking:  going for the extensive data content check (rows can be in different order).")
            debugMessage.AppendLine("checking:  getting hashcodes from dtbl_a started:  " & System.DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.ffff"))

        End If

        For current_Record = lowerBound_Records To upperBound_Records
            Dim dataRow_check As New System.Text.StringBuilder

            dataRow_check.Append("<dataRow>")
            For current_Column = lowerBound_Columns To upperBound_Columns
                Dim columnName As System.String
                Dim valueIsNull As System.Boolean
                Dim value As System.String

                columnName = dtbl_a.Columns(current_Column).ColumnName
                valueIsNull = System.Convert.IsDBNull(dtbl_a.Rows(current_Record).Item(columnName))

                If valueIsNull = False Then
                    value = dtbl_a.Rows(current_Record).Item(columnName).ToString

                Else
                    value = "[null]"

                End If

                dataRow_check.Append("<" & columnName & ">" & value & "</" & columnName & ">")

            Next current_Column

            dataRow_check.Append("</dataRow>")

            Dim newRow As System.Data.DataRow = dtbl_check(0).NewRow
            Call newRow.BeginEdit()
            newRow.Item("index") = current_Record
            newRow.Item("hashCode") = dataRow_check.ToString.GetHashCode
            newRow.Item("checked") = System.Convert.DBNull

            If debug = True Then
                newRow.Item("dataRow") = dataRow_check.ToString

            End If

            Call newRow.EndEdit()
            Call dtbl_check(0).Rows.Add(newRow)
            dataRow_check = Nothing

        Next current_Record

        If debug = True Then
            debugMessage.AppendLine("checking:  finished hashcodes for dtbl_a ended:  " & System.DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.ffff"))
            debugMessage.AppendLine("checking:  getting hashcodes from dtbl_b and cross checking using dtbl_a started:  " & System.DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.ffff"))

        End If

        For current_Record = lowerBound_Records To upperBound_Records
            Dim dataRow_check As New System.Text.StringBuilder
            Dim checked As System.DateTime

            checked = System.DateTime.Now
            dataRow_check.Append("<dataRow>")

            For current_Column = lowerBound_Columns To upperBound_Columns
                Dim columnName As System.String
                Dim valueIsNull As System.Boolean
                Dim value As System.String

                columnName = dtbl_a.Columns(current_Column).ColumnName

                Try
                    valueIsNull = System.Convert.IsDBNull(dtbl_b.Rows(current_Record).Item(columnName))

                Catch exc As System.Exception
                    result = False
                    Return result

                End Try

                If valueIsNull = False Then
                    value = dtbl_b.Rows(current_Record).Item(columnName).ToString

                Else
                    value = "[null]"

                End If

                dataRow_check.Append("<" & columnName & ">" & value & "</" & columnName & ">")

            Next current_Column

            dataRow_check.Append("</dataRow>")

            Dim selectQuery As System.String
            Dim dataRows() As System.Data.DataRow
            Dim hashCode As System.Int32

            hashCode = dataRow_check.ToString.GetHashCode
            selectQuery = "[hashCode] = " & hashCode.ToString & " and [checked] is null "
            dataRows = dtbl_check(0).Select(selectQuery)

            If dataRows.Length > 0 Then
                Call dataRows(0).BeginEdit()
                dataRows(0).Item("checked") = checked
                Call dataRows(0).EndEdit()

                Dim newRow As System.Data.DataRow = dtbl_check(1).NewRow
                Call newRow.BeginEdit()
                newRow.Item("index") = dataRows(0).Item("index")
                newRow.Item("hashCode") = dataRows(0).Item("hashCode")
                newRow.Item("checked") = checked

                If debug = True Then
                    newRow.Item("dataRow") = dataRow_check.ToString

                End If

                Call newRow.EndEdit()
                Call dtbl_check(1).Rows.Add(newRow)

            Else
                result = False

                If debug = True Then
                    debugMessage.AppendLine("checking:  finished hashcodes for dtbl_b ended:  " & System.DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.ffff"))
                    debugMessage.AppendLine("decision:  " & result.ToString & "!")
                    debugMessage.AppendLine("  reason:  a row in dtbl_b doesn't match up in dtbl_a (either due to changes or didn't exist).")
                    debugMessage.AppendLine(" dataRow:  " & dataRow_check.ToString)

                End If

                dataRow_check = Nothing

                Return result

            End If

            dataRows = Nothing
            dataRow_check = Nothing

        Next current_Record

        result = True

        If debug = True Then
            debugMessage.AppendLine("checking:  finished hashcodes for dtbl_b ended:  " & System.DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.ffff"))
            debugMessage.AppendLine("decision:  " & result.ToString & "!")
            debugMessage.AppendLine("  reason:  all " & recordCount(0) & " record(s) match up between both tables.")

        End If

    Catch exc_Exception As System.Exception
        errorMessage = exc_Exception.Message
        result = False

        If debug = True Then
            debugMessage.AppendLine("exception in dataTablesAreEqual!")
            debugMessage.AppendLine("decision:  " & result.ToString & "!")
            debugMessage.AppendLine(" message:  " & errorMessage)

        End If

    Finally
        If dtbl_check(1) IsNot Nothing Then
            Call dtbl_check(1).Clear()
            dtbl_check(1) = Nothing

        End If

        If dtbl_check(0) IsNot Nothing Then
            Call dtbl_check(0).Clear()
            dtbl_check(0) = Nothing

        End If

        If debug = True Then
            Call System.Diagnostics.Debug.WriteLine(debugMessage.ToString)

        End If

        debugMessage = Nothing

    End Try

    Return result

End Function

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Assuming the tables have the same structure (column names and data types)

static bool AreTablesEqual(DataTable t1, DataTable t2)
{
    // If the number of rows is different, no need to compare the data
    if (t1.Rows.Count != t2.Rows.Count)
        return false;

    for (int i = 0; i < t1.Rows.Count; i++)
    {
        foreach(DataColumn col in t1.Columns)
        {
            if (!Equals(t1.Rows[i][col.ColumnName], t2.Rows[i][col.ColumnName]))
                return false;
        }
    }
    return true;
}

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I have used

    bool AreEqual(DataTable d1, DataTable d2)
    {
        if (d1.Rows.Count != d2.Rows.Count)
            return false;
        for (int i = 0; i < d1.Rows.Count; i++)
        {
            var d1Row = d1.Rows[i];
            var d2Row = d2.Rows[i];
            for (int j = 0; j < d1Row.ItemArray.Count(); j++)
            {
                if (!d1Row[j].Equals(d2Row[j]))
                   return false;
            }
        }

        return true;
    }

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I would write an extension method that overrides object.Equals, takes two DataTable's and compares them with whatever criteria you want.