Skip to main content

c# - How to get index of a column by name in a DataTable


Get column index by name from a DataTable



The DataTable class represents one table of in-memory data. The DataTable objects are conditionally case-sensitive. To create a DataTable programmatically the asp.net developers must first define its schema by adding DataColumn objects to the DataColumnCollection. To add rows to a DataTable, the developers must first use the NewRow() method to return a new DataRow object. The DataTable also contains a collection of Constraint objects that can be used to ensure the integrity of the data.




The following asp.net c# tutorial code demonstrates how we can get the index of a column by the column name from a DataTable. So we have to find the index of a specified DataColumn object by its name within a DataTable instance.




Here we used the DataTable class Columns property to get its columns collection as a DataColumnCollection object. Then we used DataColumnCollection’s IndexOf() method to get the specified column’s index using the column name within the columns collections.




The DataTable class Columns property gets the collection of columns that belong to this table. The Columns property value is a DataColumnCollection that contains the collection of DataColumn objects for the table. An empty collection is returned if no DataColumn objects exist.




The DataColumnCollection class represents a collection of DataColumn objects for a DataTable. The DataColumnCollection IndexOf() method searches for the specified DataColumn and returns the zero-based index of the first occurrence within the collection.




Here we used the IndexOf(String) method overload to get the specified column index by its name within a DataTable instance. The IndexOf(string? columnName) method overload has a parameter named columnName. This parameter is a String which is the name of the column to find.




The DataColumnCollection IndexOf(string? columnName) method returns an Int32 which is the zero-based index of the column with the specified name or -1 if the column does not exist in the collection.




So finally, using the DataTable Columns property the asp.net developers can get the DataColumnCollection object. And the DataColumnCollection class IndexOf() method allows the developers to get the index of a column’s object by its name within the specified DataTable.





IndexOfMethodDataTable.aspx



<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html>
<script runat="server">
    void Button1_Click(object sender, System.EventArgs e)
    {
        DataTable dt = new DataTable();
        dt.TableName = "Books";

        DataColumn dc = new DataColumn();
        dc.ColumnName = "BookID";
        dc.DataType = typeof(int);

        DataColumn dc2 = new DataColumn();
        dc2.ColumnName = "BookName";
        dc2.DataType = typeof(string);

        DataColumn dc3 = new DataColumn();
        dc3.ColumnName = "Author";
        dc3.DataType = typeof(string);

        dt.Columns.AddRange(new DataColumn[] {dc,dc2,dc3});

        dt.Rows.Add(new object[] { "1", "Native Video in HTML5", "David Griffiths" });
        dt.Rows.Add(new object[] { "2", "Best iPhone Apps, Second Edition", "J.D. Biersdorfer" });
        dt.Rows.Add(new object[] { "3", "Microsoft® Silverlight® 4 Step by Step", "Laurence Moroney" });
        dt.Rows.Add(new object[] { "4", "Premiere Elements 8: The Missing Manual", "Chris Grover" });
        
        GridView1.DataSource = dt;
        GridView1.DataBind();

        //this line get the 'Author' DataColumn index in DataTable
        int columnIndex = dt.Columns.IndexOf("Author");
        Label1.Text = "'Author' DataColumn index in DataTable? = " + columnIndex;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to get the index of the DataColumn with the specific name from DataTable in ado.net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:DarkBlue; font-style:italic;">
            Using IndexOf() method - How to get the index of the
            <br /> DataColumn with the specific name from DataTable in ado.net
        </h2>
        <hr width="550" align="left" color="CornFlowerBlue" />
        <asp:GridView 
            ID="GridView1"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="525"
            HeaderStyle-BackColor="DarkOrchid"
            RowStyle-BackColor="SlateBlue"
            AlternatingRowStyle-BackColor="MediumSlateBlue"
            >
        </asp:GridView>
        <br /><br />
        <asp:Label
             ID="Label1"
             runat="server"
             Font-Size="Large"
             ForeColor="IndianRed"
             >
        </asp:Label>
        <br /><br />
        <asp:Button 
            ID="Button1"
            runat="server"
            OnClick="Button1_Click"
            Text="Populate GridView"
            Height="45"
            Font-Bold="true"
            ForeColor="DarkBlue"
            />
    </div>
    </form>
</body>
</html>





Labels:

Popular posts from this blog

Restricting Jetpack Compose TextField to Numeric Input Only

Jetpack Compose has revolutionized Android development with its declarative approach, enabling developers to build modern, responsive UIs more efficiently. Among the many components provided by Compose, TextField is a critical building block for user input. However, ensuring that a TextField accepts only numeric input can pose challenges, especially when considering edge cases like empty fields, invalid characters, or localization nuances. In this blog post, we'll explore how to restrict a Jetpack Compose TextField to numeric input only, discussing both basic and advanced implementations. Why Restricting Input Matters Restricting user input to numeric values is a common requirement in apps dealing with forms, payment entries, age verifications, or any data where only numbers are valid. Properly validating input at the UI level enhances user experience, reduces backend validation overhead, and minimizes errors during data processing. Compose provides the flexibility to implement ...
Read more

jetpack compose - TextField remove underline

Compose TextField Remove Underline The TextField is the text input widget of android jetpack compose library. TextField is an equivalent widget of the android view system’s EditText widget. TextField is used to enter and modify text. The following jetpack compose tutorial will demonstrate to us how we can remove (actually hide) the underline from a TextField widget in an android application. We have to apply a simple trick to remove (hide) the underline from the TextField. The TextField constructor’s ‘colors’ argument allows us to set or change colors for TextField’s various components such as text color, cursor color, label color, error color, background color, focused and unfocused indicator color, etc. Jetpack developers can pass a TextFieldDefaults.textFieldColors() function with arguments value for the TextField ‘colors’ argument. There are many arguments for this ‘TextFieldDefaults.textFieldColors()’function such as textColor, disabledTextColor, backgroundColor, cursorC...
Read more

jetpack compose - Image clickable

Compose Image Clickable The Image widget allows android developers to display an image object to the app user interface using the jetpack compose library. Android app developers can show image objects to the Image widget from various sources such as painter resources, vector resources, bitmap, etc. Image is a very essential component of the jetpack compose library. Android app developers can change many properties of an Image widget by its modifiers such as size, shape, etc. We also can specify the Image object scaling algorithm, content description, etc. But how can we set a click event to an Image widget in a jetpack compose application? There is no built-in property/parameter/argument to set up an onClick event directly to the Image widget. This android application development tutorial will demonstrate to us how we can add a click event to the Image widget and make it clickable. Click event of a widget allow app users to execute a task such as showing a toast message by cli...
Read more