Skip to main content

c# - How to set maximum size of a column in a DataTable

Set the maximum size of a DataColumn in 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 set the maximum size of a DataColumn in a DataTable instance. Here we used the DataColumn class MaxLength property to set the maximum size/length of a DataColumn in a DataTable object.

The DataColumn class MaxLength property gets or sets the maximum length of a text column. The MaxLength property value is an Int32 which is the maximum length of the column in characters. If the specified column has no maximum length, the property value is -1 and this is the default value.

But the DataColumn MaxLength property is ignored for non-text columns. The ArgumentException exception is raised if the asp.net developers assign MaxLength to a non-string column.
DataColumnMaxLengthProperty.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);
        dt.Columns.Add(dc);

        DataColumn dc2 = new DataColumn();
        dc2.ColumnName = "BookName";
        dc2.DataType = typeof(string);
        //this line make DataColumn values maximum length 40 characters
        dc2.MaxLength = 40;
        dt.Columns.Add(dc2);

        DataColumn dc3 = new DataColumn();
        dc3.ColumnName = "BookAuthor";
        dc3.DataType = typeof(string);
        dt.Columns.Add(dc3);

        dt.Rows.Add(new object[] { 1, "Programming Python, Fourth Edition", "Mark Lutz" });
        dt.Rows.Add(new object[] { 2, "Head First Python", "Paul Barry" });

        /*uncomment this line to get error message because 
        BookName column maximum length 40 characters*/
        //dt.Rows.Add(new object[] { 3, "Hadoop: The Definitive Guide, Second Edition", "Tom White" });

        dt.Rows.Add(new object[] { 4, "Real World Instrumentation with Python", "John M. Hughes" });

        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to use DataColumn MaxLength Property in ado.net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:DarkBlue; font-style:italic;">
            How to use DataColumn MaxLength Property in ado.net
        </h2>
        <hr width="525" align="left" color="CornFlowerBlue" />
        <asp:GridView 
            ID="GridView1"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="550"
            >
            <HeaderStyle BackColor="Crimson" ForeColor="Snow" Height="30" />
            <RowStyle BackColor="SaddleBrown" ForeColor="Snow" />
            <AlternatingRowStyle BackColor="Tan" ForeColor="Snow" />
        </asp:GridView>
        <br />
        <asp:Button 
            ID="Button1"
            runat="server"
            OnClick="Button1_Click"
            Text="Populate GridView"
            Height="45"
            Font-Bold="true"
            ForeColor="DodgerBlue"
            />
    </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