How Can I Change a DataTable Column's DataType After Data Has Been Populated?

Change DataColumn data type in DataTable

When working with data in a DataTable, you may encounter situations where you need to modify the data type of a specific column to accommodate a different data format.

Consider the following scenario: a DataTable is populated with data from a SQL table and the first column, originally defined as a 'Double' data type, needs to be converted to an 'Int32'.

Code snippet:

<code class="language-csharp">DataTable dt = new DataTable();
using (SqlConnection conn = new SqlConnection(...))
{
    using (SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM " + tableName, conn))
    {
        adapter.FillSchema(dt, SchemaType.Source);
        adapter.Fill(dt);
    }
}</code>

Solution:

By default, DataTable does not allow modifying the data type of a column after filling it with data. However, there is a workaround to clone the DataTable and modify the data type of the columns. The modified columns can then be repopulated with data from the original table.

Code snippet:

<code class="language-csharp">// 创建一个具有所需列数据类型的克隆 DataTable
DataTable dtCloned = dt.Clone();
dtCloned.Columns[0].DataType = typeof(Int32);

// 使用原始表中的数据填充克隆表
foreach (DataRow row in dt.Rows)
{
    dtCloned.ImportRow(row);
}</code>

With this approach, you can effectively change the data type of a column even after filling the DataTable with data.

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